Optical capsule and spectroscopic method for treating or diagnosing the intestinal tract

ABSTRACT

A device and method for mapping, diagnosing and treating disorders or other diseases, disorders or conditions (e.g., bleeding, ischemic or necrotic tissue, and presence of certain chemicals or substances) of the intestinal tract is provided using a capsule passing through the intestinal tract and sensing optical characteristics as the capsule passes through. Further, a capsule tracking system is provided for tracking a capsule&#39;s location along the length of an intestinal tract as various treatment and/or sensing modalities are employed. In one variation, an acoustic signal is used to determine the location of the capsule. A map of optical characteristics may be derived from the pass of a capsule to diagnose the disorder or disease. The capsule or subsequently passed capsules may treat, further diagnose or mark the intestinal tract at a determined location along its length.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part of U.S. applicationSer. No. 09/892,404 filed on Jun. 26, 2001, and claims priority overProvisional Application Serial No. 60/436,285, filed on Dec. 24, 2001.

FIELD OF THE INVENTION

[0002] This invention relates to a device and method for mapping,diagnosing and treating the intestinal tract using a capsule passingthrough the intestinal tract. Further, this invention relates to acapsule tracking system for tracking a capsule's location, including fortracking a corresponding diagnosis or treatment, along the length of anintestinal tract. The invention also relates to a method and device fordiagnosis and/or treating the gastrointestinal tract using such acapsule and in such a tracking system to detect optical characteristicsusing spectroscopy, within the intestinal tract, for example, contents,substances, chemicals, toxins and tissue conditions of or within theintestinal tract. This invention also relates to a method and device forlocating and treating bleeding in the intestinal tract.

BACKGROUND OF THE INVENTION

[0003] Different areas of the intestinal tract have varying degrees ofsurgical accessibility. For example, there has been great difficulty indiagnosing and treating disorders in the human colon and small intestinebecause of the length of the small intestine (typically about 21 feet or7 meters), and its inaccessibility. Also certain regions of the colonhave proven difficult to access for treatment. Accordingly, it would bedesirable to provide a less or minimally invasive device for diagnosingor treating difficult to access portions of the intestinal tract, suchas, the small intestine and colon.

[0004] One condition that is particularly difficult to locate within theintestinal tract is intestinal bleeding. Intestinal bleed can occur fora number of different reasons. Currently intestinal bleeding can bedetected by blood in the stool. However, location, cause and treatmentare currently difficult. It would be desirable to provide an effectivemeans for locating and treating bleeding in the intestinal tract.

[0005] Certain chemicals in the intestinal tract may be indicative aparticular disease or condition. Various cancers produce protein markersor other compounds that are particular to the cancer. Other abnormalchemicals or toxins or abnormal quantities of such chemicals or toxinsmay be secreted into the intestinal tract by bacteria or may be producedby abnormal or diseased tissue or as a biological response to thepresence thereof. Such chemicals and toxins are difficult to identifyand locate within the intestinal tract, particularly in the smallintestine which is relatively inaccessible and has a tortuous anatomy.Accordingly, it would be desirable to provide a method and device foridentifying and locating such chemicals or toxins in the intestinaltract. Similarly it is difficult to locate diseased tissue in theintestinal tract, such as, cancerous, pre-cancerous, inflamed, necrotic,and ischemic tissue, etc.

[0006] Swallowable telemetry capsules have been used in a number oftreatment and diagnostic applications. Some swallowable capsules havebeen proposed to deliver medication to specific areas of the intestinaltract where the release of the medication is actuated by an external RFsignal received by the capsule. The signal actuates an electromechanicaldevice within the capsule to release the medication. Similarly, somecapsules have been proposed to acquire samples from the intestinal tractwhere actuation of an electromechanical sampling device is remotelycontrolled and the capsule is then retrieved when excreted. Othercapsules have been proposed, for example, to take pictures or videoimages, or measure pH, pressure or temperature. An autonomous capsulewith electrodes has been proposed to provide electrical stimulationwhile moving through the GI tract to restore motor evacutory function ofthe GI tract. Such a device has been proposed to propel a capsulethrough the gut.

[0007] Telemetry treatment and/or diagnostic capsules with mappingcapabilities have been proposed to identify a target treatment site on athree-dimensional map of the intestinal tract. Generally, the proposedsystems include capsules that transmit RF signals to externally locatedantennas. The relative amplitudes of the RF signals received by theantennas are used to determine relative location of the capsule based onthe correlation between the capsule to antenna distance and RF amplitude(signal strength). According to these proposed systems, using four ormore antennas and triangulation techniques, the location of the capsulein two or three-dimensional space is determined based on RF amplitude.From the location information, a map of the capsule's path in space maybe created. In subsequent passes of the capsule through the intestinaltract, the capsule is used for treatment or diagnosis purposes at atarget location. In addition, it has been proposed to use video imagesin combination with such RF determined spatial information to identify atarget location in first and subsequent capsule passes.

[0008] A capsule with a mechanical cogwheel has been proposed tocalculate the small bowel length and small bowel transit velocity. Thedevice relies on the turning of the cogwheel by contact with theintestinal wall during small bowel transit, to calculate centimeters oftravel.

[0009] Many disadvantages are inherent in the current capsule trackingtechniques. Tracking systems using RF amplitude data from signalstransmitted through body tissue have a high degree of error andinadequate resolution for accurate intestinal tract mapping. (With 1 cmintestinal diameters and substantial overlap of intestines, an accurateresolution is necessary.) The resolution problems are due to a number ofpossible inaccuracies, which are compounded because RF signal strengthover distance varies in a non-linear fashion. RF signal is directional,and thus its strength varies with the direction of the signal or theorientation of the coil transmitter with respect to the fixed coilreceiver. Thus, without any change in location, a change in orientationmay cause a dramatic change in RF amplitude at the antenna. Further, RFtransmission is absorbed by tissue, particularly at higher frequencies.Thus the larger coils that would be required to transmit lower frequencyRF signals, constrain the ability to miniaturize an optimal device.

[0010] In addition to RF resolution issues, due to movement and shiftingof the intestinal organs within the abdomen, 3D mapping may notrepeatably identify a precise location within the intestines when asubsequent capsule is passed through the tract. The intestinal organstend to shift with the filling or emptying of the various portions ofthe digestive system, and they tend to move with peristalsis. Apatient's abdomen also moves with respiration and change in patientposition. Thus, given the intestinal shifting along with the intestine'ssmall diameter and overlap, the 3D tracking system may identify thewrong portion of the intestinal tract when a later capsule passesthrough. Therefore, it would be desirable to provide a tracking systemthat accurately and repeatably identifies a desired location in theintestinal tract so that a location identified by a first capsule issubstantially the same as a location identified by a subsequently passedcapsule. It would also be desirable to provide a capsule and trackingsystem that does not rely on RF transmission amplitude data for accuratetracking.

[0011] As noted above, telemetry capsules have been used in therapeuticand diagnostic applications. Such therapeutic and diagnostic deviceshave typically involved providing medication to a location in theintestinal tract alone or in combination with sampling the fluids of theintestinal tract. The pH, temperature and pressure have also beenmeasured. It would be desirable to provide capsules with new diagnosticand treatment modalities, particularly in a manner that would combinethe treatment with tracking and diagnostic capabilities, to treatdifficult to access regions of the intestinal tract.

[0012] One clinically significant condition that has been challenging totreat in the intestines is bleeding. Location of bleeding in theintestinal tract is very difficult to identify and requires surgicalintervention to correct if it persists. Therefore, it would be desirableto provide a method and device for identifying a location of intestinalbleeding and for treating the location in a less invasive manner.

[0013] Another diagnostic/therapeutic area of interest is in identifyingblockages or other diseased portions of the intestine and the ability tobiopsy the specific location where there is such a blockage or disease.It would also be of interest to assist a surgeon in specifically markinga site for surgery prior to surgical intervention for easieridentification of the site.

[0014] Another clinically significant parameter is the transit time ofmaterials through the intestines. Current techniques in measuringtransit time involve ingesting a material that reacts with the contentsof the colon such that the patient's breath gives off a detectable gasat such time. This technique is not very precise and does not provideinformation on, e.g., which particular portion of the tract isresponsible for transit abnormalities. Some patients have segmentaldiseases where a segment of the intestine does not have adequatemotility. Thus, velocity of travel of materials through various portionsof the intestine would be of interest in determining where there may besegmental disease.

[0015] Motility disorders in some situations relate to abnormalities inthe periodic, coordinated contractile activity of the smooth musclesassociated with the intestinal tract. Various organs of the intestinaltract such as the stomach, small intestine and colon contain cells thatare believed to govern the organs—periodic contractile behavior. Inhealthy humans, in certain intestinal tract regions, these cellsgenerate and propagate rhythmic electrical signals. In general, severaltypes of electrical potential activities have been observed in theintestinal tract. Consistent slow wave or pacesetter potentials havebeen observed and higher frequency spike activity has been observed. Thepacesetter potentials are continuously propagating, relatively lowfrequency, cyclic depolarizations of the smooth muscle lining. Thehigher frequency spike bursts tend to correspond with smooth musclecontractile activity including segmentation and peristalsis. In general,when the spike burst activity occurs, it appears to be at a fixed timedelay with respect to the slow wave potentials. It is believed that whenthe pacesetter potentials are combined with a chemical or neuralexcitation of the cells, smooth muscle contractile activity may occurand that the pacesetter potentials control and coordinate the frequencyand direction of the contractions.

[0016] Accordingly, it would be of interest to provide a means forobserving the electrical activity such as, for example, the vagal nerveactivity, the electromyogram, or of the intestinal smooth muscle layers,etc., to determine whether the electrical activity is abnormal,indicating possible disease.

[0017] Electrical stimulation of the gastrointestinal tract has beenproposed to treat motility related disorders and other gastrointestinaldiseases. The electrical stimulation has been proposed in a number offorms, such as, e.g., pacing; electrical contractile stimulation orother stimulation; e.g., to treat nausea. Electrical pacing of theintestinal tract is generally defined as periodic electrical stimulationthat captures and/or controls the frequency of the pacesetter potentialor slow wave activity of the intestinal organ (including in a retrogradedirection). Electrical contractile stimulation generally refers tostimulation that directly causes or results in muscular contractionassociated with the intestinal tract.

[0018] In some disease states, dysrhythmias of the intestinal tractpacesetter potentials may be present. Electrical pacing of pacesetterpotentials has been proposed to induce regular rhythms for thepacesetter potentials with the intent of inducing regular or controlledintestinal tract contractions. Pacing has also been suggested to causeretrograde propagation of pacesetter potentials. Also, electricalcontractile stimulation of the intestinal tract has been proposed toinduce peristalsis.

[0019] Many currently proposed intestinal tract electrical stimulationprocedures are relatively invasive and require accessing the intestinaltract through the abdomen, e.g., in an open or a laparoscopic procedure.The devices used typically require implanting permanent leads,electrodes and a pacemaker within the body. Therefore, it would bedesirable to provide a less invasive device for electrically stimulatingthe intestinal tract, particularly in combination with a system fortracking the device and delivering the treatment to an identifiedlocation.

SUMMARY OF THE INVENTION

[0020] The present invention provides a capsule having diagnostic and/ortreatment capabilities, and a system for tracking the capsule throughthe intestinal tract. One embodiment of a tracking system provides animproved system for determining the coordinates of a capsule inthree-dimensional space. According to this embodiment, an acousticsignal is transmitted between a capsule as it is passing through theintestinal tract, and a location external a patient's body. As such anacoustic transmitter or transmitters are located either at the capsuleor location external to the patient's body and the acoustic receiver(s)or sensor(s) are located at the other of either the capsule or locationexternal a patient's body. The velocity of an acoustic signal throughtissue is predictable (ultrasound transmits through tissue at about 1540meters per second). Using the amount of time the signal takes to travelto the receiver(s) and the signal velocity, the relative capsuledistance(s) to the location(s) external the patient's body isdetermined. Also, it should be noted that the transit time of theacoustic signal is linearly proportional to the distance traveled.

[0021] In one preferred embodiment, a capsule passing through theintestinal tract transmits an acoustic signal through the body to aplurality of externally located acoustic sensors. The relative capsuledistances to the sensors are determined using the amount of time thesignal takes to travel to the receiver. Triangulation of the comparativedistances will result in a location of the capsule in space (forexample, on a Cartesian coordinate system).

[0022] According to a preferred embodiment, a reference signal is usedto identify the time of acoustic signal origination. In one variation,the reference signal may be in the form of an RF reference signaldelivered from the capsule to an external sensor where the capsule emitsthe acoustic signal. In this variation, the RF reference signal isdelivered at predetermined time from the emission of the acousticsignal. The RF signal, which travels at the speed of light, is receivedby the sensors relatively instantaneously. The RF signal is used by thesensor/receiver to determine when the acoustic signal was transmitted.Alternatively, in another variation, an external, telemetricallydelivered electromagnetic control signal may be used to trigger theemission of the acoustic signal from the capsule, thereby providing atime reference. Where the acoustic transmitter is at located externallyof the patient, the reference signal, for example, may also be a triggersignal that triggers emission of the acoustic signal from and externaltransducer. In various other embodiments, the reference signal mayutilize other communication media to provide a reference signal. Forexample, an infra-red link or a distributed resistive link could beused. According to these alternative embodiments, signals may betransmitted either to or from the capsule.

[0023] Another embodiment provides a tracking system that tracks acapsule's linear position along the intestinal tract length or a portionthereof. As the capsule moves through the tract, it senses diagnosticinformation. The tracking system correlates sensed diagnosticinformation with the capsule's corresponding linear position when theinformation is sensed. From the diagnostic information, a location alongthe length traveled is identified for treatment, or therapeuticfunctions, which also include acting on the intestinal tract for atherapeutic purpose, e.g. to mark the location for surgicalintervention. A location along the length may also be identified forfurther diagnosis, including using subsequently passed capsules.

[0024] In a subsequent pass of a capsule, the capsule's linear positionis monitored until it reaches the position along the length identifiedby a previous capsule. At that location, the subsequent capsule thenprovides, treatment, further diagnosis, or marking. Because theintestinal tract length is relatively constant, the tracking systemprovides a means for locating a portion of the intestinal tract that isrelatively independent of intestinal tract shifting or movement. Thus,the system also provides repeatable tracking independent of the locationof the sensors or pods on the patient. The system of this embodimentthus allows for subsequent passes of the capsule where the sensors orpods have been repositioned, for example in a later treatment cycle. Ina preferred embodiment, the sensors are provided with the ability toactively locate each other in a three dimensional coordinate system.This allows the sensors to re-calibrate to determine their relativelocation when they have moved due to respiration, or other patientmovement. Because the location of the capsule in a preferred embodimentof the tracking system depends on the relative location of the sensors,re-establishing the relative sensor location on a regular basiscompensates for sensor movement during a procedure using tracking.

[0025] Preferably, the position of a capsule along a length of theintestinal tract is determined by first identifying the capsule's3-dimensional position over time, for example, on a Cartesian coordinatesystem created by the pods. The tracking system includes a processorthat monitors the signals from the pods and that uses incremental changein position over time to convert the 3D capsule location information tolinear travel distance measurements. The linear travel distancemeasurements are then used to derive the capsule's position along thelength of the intestinal tract portion of interest. Preferably thetracking system uses acoustic transmission time from the capsule toexternal sensors to determine the capsule's 3D coordinates as describedherein. An initial location of the capsule is preferably firstidentified, such as, when it reaches the pylorus. Such position may bedetermined by a number of means such as by determining capsule movementindicative that the capsule is moving from the stomach into the smallintestine, including, for example change in location, or acceleration.Alternatively a capsule's initial location may be determined, forexample by pressure, which changes when the capsule passes through thepylorus, or pH, which changes when the capsule enters the duodenum.

[0026] Another feature of the invention provides a system to compensatefor variations in capsule location determinations along the length ofthe intestinal tract that are due to intestinal smooth musclecontractions and corresponding foreshortening of the intestinal tract.For example, pressure may be measured to determine the relativerelaxation/contraction of the tract and the correspondingforeshortening. The determination of capsule location may be a factor ofsuch pressure. Another feature of the invention provides a filter thatdetects and filters out capsule movement not corresponding to actualmovement along the length of the tract. For example, by observing theorientation and type of movement, movement that is not statisticallyrelated to movement along the intestinal length may be filtered out.

[0027] Another feature of the invention is a capsule having a pluralityof acoustic transducers to provide information concerning directionalorientation of the capsule.

[0028] Although the linear tracking system may not require sensing ofadditional parameters to determine location, the linear tracking is usedas a diagnostic tool when combined with other sensed information toprovide a diagnostic linear map of the intestinal tract or a portionthereof (such as the small intestine.) Further, the tracking system ispreferably combined with both diagnostic and treatment functions. Inuse, after a diagnostic capsule provides a diagnostic linear map of theintestinal tract, a treatment capsule is passed through intestinal tractportion. The treatment capsule that travels through the intestinal tractis monitored by the tracking system for its relative linear positionuntil it reaches a position along the intestinal tract length to betreated. The mechanism for providing the treatment is then actuated,typically by a telemetrically delivered control signal.

[0029] A number of capsules may be used as a combined diagnostic andtreatment system. For example, a first capsule obtains information onthe capsule position along the intestinal length and correspondingdiagnostic information (if desired, a diagnostic linear map of thetract). Another capsule may then be passed through the tract to providetreatment and/or diagnosis at a desired location along the length of thetract. Once the length of the tract has been mapped, any number ofsubsequent capsules may be passed through to further obtain diagnosticinformation or to provide treatment. Using this technique a clear map ofdiagnostic information vs. length of intestine may be obtained.Additional capsules may be used at a later time using the same map foradditional diagnosis, treatment or follow up. Also a combination ofcapsules may be swallowed in a spaced apart sequence where more than onecapsule is in the digestive system at one time.

[0030] A diagnostic capsule may sense a number of parameters such as,for example, pH for assessing acidity levels in the intestinal tract,electrical activity, electrical impedance, optical parameters fordetection of specific reflected or transmitted light spectra, e.g.blood, objects or obstructions in the intestinal tract, pressure forintestinal tract manometric data acquisition and various diagnosticpurposes such as determining effectiveness of stimulation, blockages orconstrictions, etc. An acoustic transducer, for example, piezoelectriccrystals, may be used for performing diagnostic ultrasound imaging ofthe intestinal tract etc. Also, a temperature transducer may be used.Also, from the positional information over time, capsule transit time,velocity, and acceleration may be calculated and used to identifylocations or segments of the intestine where there are motilitydisorders (such as segmental diseases).

[0031] A treatment capsule with the described tracking systemsubsequently passing through the identified portion to be treated willbe signaled to provide treatment. The treatment capsule may include butdoes not require any diagnostic sensors. The treatment capsules mayperform one or more of a number of treatment functions. Such treatmentmay take several forms or combinations that may include, for example,delivering an electrically stimulating signal, treating bleeding withablation, clotting agents or coagulants, active or passive drug deliveryor gene therapy treatment at specific portions of the tract, aninflatable element for performing balloon plasty of the intestinaltract, for placing a stent (e.g. for strictures), a self expanding stentdelivery system, tissue biopsy or content sampling devices, or markingdevices, (e.g. staining, marking or tattooing ink, such as india ink,methylene blue or purified carbon powder; radiopaque dye; or magneticdevices) e.g., for locating a portion of the tract for surgery, etc.

[0032] One embodiment of the capsule system includes a sensor fordetecting the presence of blood. For example, an optical sensor or achemical sensor may be provided that senses the presence of blood. Thecapsule is passed through the intestine and the location of the capsulealong the length of the tract where the blood is sensed is identified. Atreatment capsule having bipolar electrodes is then passed through theintestinal tract until it reaches the identified length of the tractwhere bleeding is occurring. An external power source is coupled to anRF coil within the capsule to deliver a current through the electrodesto ablate or cauterize the bleeding tissue. Alternatively, a site wherebleeding is present may be treated using a subsequently passed capsulehaving a balloon tamponade, i.e. an inflatable member that usescompression and/or a thrombogenic substance coated on the inflatablemember to help cause hemostasis.

[0033] Another embodiment of the capsule system comprises a diagnosticcapsule that includes a sensor (such as a pressure sensor) thatidentifies a blockage, stricture or narrowing of the intestine. Thelocation of the capsule along the length of the intestine is tracked.The sensed blockage is correlated to the capsule's linear position alongthe intestinal tract. The tracking system tracks the linear position ofa treatment capsule as it passes through the tract until it reaches thelocation of the blockage. An externally transmitted telemetric signalcauses a balloon plasty capsule to deploy an expandable member thatdilates the intestinal passage. In one variation, a variable sizeballoon may be used to determine the extent of a blockage. In thisvariation, for example, a balloon may be inflated at the suspectedblockage area. The balloon is gradually deflated until it passes throughthe blocked area. The diameter of the balloon when the balloon is ableto pass through the constricted site may, e.g., be used to determineextent of the blockage. The diameter of the balloon may be approximatedfrom the volume of inflation medium in the balloon. In another variationa balloon may be provided with an expandable support structure over theballoon such as a stent. The stent may be deployed within the intestinaltract when the balloon is expanded and thereby provide additional radialsupport of the intestinal wall.

[0034] Another embodiment of the capsule system provides a diagnosticcapsule for which position and corresponding diagnostic information aretracked along the length of the intestinal tract. A location forsurgical intervention is identified based on the diagnostic informationand a second capsule is passed through the tract. When the secondcapsule reaches the linear position of the location for surgicalintervention, a telemetric signal is delivered from an external devicethat triggers the release of a marker within the tract at the desiredlocation. Such marker may include, for example a radiopaque marker thatmay be located with an x-ray system during a procedure, a fluorescingcompound that is used to identify the location (e.g., fluorescein), or adye that stains through the wall of the intestine (e.g. staining,marking or tattooing ink, such as india ink, methylene blue or purifiedcarbon powder, radiopaque dye). The markers may assist a surgeon in alaparoscopic or open procedure where such imaging systems are usedduring the procedure or where visualization is possible, e.g. of astain.

[0035] In an alternative embodiment, a capsule may be used to mark alocation in the intestinal tract by affixing itself to the intestinalwall at an identified location. Such capsule may include deployableanchor mechanisms where an actuation mechanism causes the anchor todeploy. For example, an external telemetric command signal may triggerthe release of such anchor. Such anchor may be provided in a number offorms including an expandable member, or other wall engaging mechanism.The capsule may also be provided with a light emission source such as alaser or an IR source, that emits light to enable location of thecapsule, preferably when the capsule is affixed to the intestinal wall.

[0036] Another embodiment of the treatment capsule system is aningestible capsule that will electrically stimulate a predeterminedportion of the intestinal tract. Electrical stimulation is generallydefined herein to mean any application of an electrical signal or of anelectromagnetic field to tissue of the intestinal tract for atherapeutic purpose or to obtain diagnostic information. According tothis embodiment, electrical signals are delivered to intestinal tracttissue by at least one electrode, preferably a bipolar electrode pair,or one or more selected electrode pairs coupled to the capsule thatelectrically stimulates the intestinal tract as the capsule passesthrough it. The electrodes deliver a signal that is designed to causedesired therapeutic effect, for example, a smooth muscle response, i.e.,stimulation or inhibition of contraction or peristaltic motion. Theelectrodes may deliver the electrical stimulation to the smooth muscleby contacting, for example, the tissue that forms the intestinal liningor the mucosal tissue of the intestinal tract.

[0037] In one preferred treatment method, the electrical stimulationsignal entrains a slow wave signal of a portion of the intestinal tractsmooth muscle that is clinically absent, weak, of an undesirablefrequency, sporadic or otherwise not optimal. Also, the capsule maytransmit other electric stimuli. In one embodiment the electricalstimulus is designed to trigger the spike burst electrical activity ofthe smooth muscle associated with smooth muscle contractions. Thestimulating signals may also be designed to inhibit the inherent smoothmuscle pacing potentials, to reduce smooth muscle contractions. Thesignals may also be designed to disrupt the natural waveform andeffectively alter the existing or inherent pacing.

[0038] The stimulation electrodes provide stimulation either by way of apreprogrammed generator or one that is programmed while the capsule isin the intestine, e.g., based on sensed parameters or response tostimulation. In one embodiment, the capsule acts as a slave to anexternal device providing master stimulation signals that are receivedby the capsule and delivered to the tissue.

[0039] The stimulation capsule of the present invention may include aplurality of electrodes that may be utilized for forward or backwardelectrical stimulation, e.g., where the order in which a series ofelectrode pairs are activated can cause peristalsis to move in adirectional manner. A plurality of electrode or bipolar electrode pairsmay be provided. Such electrodes, electrode pairs or combination ofelectrodes or electrode pairs may be selected for delivering stimulationpulses, (either preprogrammed or programmed while the electrodes aredeployed in the intestine) to optimize various parameters, e.g.impedance, current density, optimal tissue contact, etc.

[0040] The capsule is swallowed or alternatively deliveredendoscopically to a predetermined portion of the intestinal tract. Thecapsule is sized and has a conformity such that it can then readily passthrough the intestinal tract. For example, the capsule may pass from thestomach to the small intestine to the colon and exit from the intestinaltract through a bowel movement, permitting its recovery if desired.Also, the capsule may, in general, move with the food material as itpasses through the intestinal tract.

[0041] The capsule is preferably provided with RF or other signaltransmission capabilities, e.g., light. The signal transmission may beused in a number of manners. As described above, the system may have RFsignal transmission capabilities that enable determination of a locationof the capsule by providing a reference for the time of the acousticsignal initiation.

[0042] The signal transmission capabilities may also be used fortelemetric communication between the capsule and an external device,e.g., to communicate data to the external device or to receiveadditional capsule programming information, command signals, orstimulation signals from the external device.

[0043] The capsule may be used to sense electrical parameters. Forexample the capsule electrodes can be used to sense native pacesetterpotential (slow wave activity) as well as spike burst activity whichcorresponds to muscular contractions. The electrodes may also be used todetermine tissue impedance. By recording the electrically sensed signalsand combining that information with tracking information, acomprehensive knowledge of the electrical behavior of the intestinaltract can be gained. Information such as absence of slow wave activity,slow wave frequency, presence of spike burst activity, number of spikeburst events per slow wave, and spike burst frequency can assist theclinician in detection and pinpoint location of various disorders suchas intestinal neuropathy, tachyarrhythmia, ileus, etc. Preferably theelectrical characteristics are correlated to the capsule's movementalong the length of the tract to provide a diagnostic linear map of theintestinal tract.

[0044] A number of capsules may be passed through in series so that thecapsules follow each other in short spaced time intervals. A firstcapsule provides diagnostic information correlated to the capsule'sposition along the length of the intestine. A subsequent capsule mayprovide electrical stimulation based on the sensed conditions. A numberof capsules may be passed through, each time obtaining diagnosticinformation or providing treatment according to the linear map.

[0045] The electrical stimulation capsule may be provided with one ormore sensors for sensing various conditions in the intestinal tract.Also, the information obtained by the sensors may by communicated viatelemetry to a control or locating device that evaluates the sensedinformation and sends a control signal to the capsule in response,instructing the capsule to perform a particular function or may providesuch stimulation signals to the capsule to be delivered through theelectrodes on the capsule. The capsule may combine the electricalstimulation feature with other therapeutic or diagnostic capsulefunctions such as, for example, drug delivery, biopsy or other materialsample recovery, etc. Finally, the sensed parameter may be used toascertain whether or not the stimulated portion is contracting inresponse to electrical stimuli received from the capsule. For example,the pressure or change in pressure within the tract at a particularlocation may be indicative of a contractive response to electricalstimulation.

[0046] As an alternative to relying on the tracking system describedherein, an electrical stimulation capsule may respond to the sensedinformation by performing a function, such as, for example, byinitiating, altering or ceasing delivery of stimulation signals uponsensing of electrical activity, pressure or pH conditions that identifythe location of the capsule or condition of the intestinal tract at thelocation.

[0047] In a variation, the inventive capsule includes an encasing atleast a portion of which is dissolvable in fluids in the intestinaltract. The encasing may selectively dissolve depending on the pH of thetract. For example, the encasing may dissolve in the small intestinewhere the pH is substantially neutral in comparison to the acidicstomach conditions. Dissolving the encasing may release a componentcontained within the capsule for example, so that encased electrodes areexposed or deployed at a desired location.

[0048] Another feature of the invention is a capsule having thecapability of functioning regardless of the directional orientation inthe intestinal tract.

[0049] In a preferred embodiment, the capsule and method described aboveare used in stimulating the small intestine. One variation of thisembodiment provides for small intestine pacing.

[0050] In another embodiment of the invention, a capsule system is usedto identify existence and/or the location of bleeding within theintestinal tract using spectroscopy by detecting light absorption,reflectance or excitation characteristics that correspond to blood andmore particularly in one embodiment, to the hemoglobin molecule. Acapsule with a light source and detectors illuminates the intestinaltract (i.e., either the tissue or the contents thereof) and then detectsthe resulting absorption or reflectance of light or the excitationcharacteristics of the intestinal tract at a location. According to oneembodiment of the invention, a capsule while being tracked in theintestine, emits and detects light or absence of light of certainwavelengths. According to this embodiment, the capsule includes at leastone light source, e.g. an LED that emits either a white light or lightof one or more particular wavelengths. The capsule further includes atleast one sensor for sensing reflected light. The sensor is coupled to aprocessor either within the capsule or via a telemetry coil or othertransmitting member. The processor determines whether or not there isbleeding present based on the sensed reflected light. The reflectedlight indicates particular absorption or reflectance of certainwavelengths of light. The system identifies the location of the capsule,for example, as described herein using acoustic signals, and in oneembodiment, the location of the sensed bleeding is determined. Asubsequent capsule may be passed through the intestine to treat, furtherdiagnose, or mark the intestine at the identified location. For examplea cauterizing chemical may be released at the location where the bloodis sensed or an electrocautery capsule may be used to cauterize orablate bleeding tissue or a marker may be released or the capsule may beanchored at the site. In another embodiment, a map of light reflectanceor absorption along the length of the intestine may be created.According to the map, the existence of bleeding may be identified alongwith its location along the length. The map may be used for diagnosisand for locating a treatment capsule or marking capsule along theintestine length. Alternatively, the optic capsule itself may mark,treat or further diagnose the location where blood is detected.

[0051] In another embodiment, a optic capsule similar to that describedabove with respect to blood detection may be used to detect the presenceof other chemicals or toxins. The chemicals or toxins such as a proteinproduced by a cancerous tissue, or a toxin produced by bacteria, havecharacteristic light absorption, reflectance or excitation properties.Similar to the detection of blood, the location of the chemicals ortoxins may be determined and subsequent treatment diagnosis or markingmay be provided with another capsule. The location may also be mapped bymapping the light absorption, reflectance or excitation. Alternatively,the optical capsule itself may mark, treat or further diagnose inresponse to detecting the chemical or toxin.

[0052] In another embodiment, a capsule is used to diagnose and/or treatother gastrointestinal diseases, conditions or disorders where thediseased tissue has a particular optical absorption, reflectance orexcitation characteristic. For example, necrotic or ischemic tissue hasabsent or diminishing blood flow. Lack of blood in the tissue may beindicated by a change in absorption of light at a specific wavelength orwavelengths, e.g. 600 nm, as compared to that of healthy tissue. Thechange in absorption may illustrate presence of deoxygenated hemoglobinversus oxygenated hemoglobin. According one embodiment of the inventiona capsule similar to that described above with respect to blooddetection, is tracked in the intestine as it emits and detects light orabsence of light of certain wavelengths. The capsule system detects whenthe tissue is not healthy or lacks blood flow and identifies thelocation of the capsule, for example, as described herein using acousticsignals. The location of the diseased or abnormal tissue along thelength may be determined and a subsequent capsule may be passed throughthe intestinal tract to treat, further diagnose or mark the tissue. Amap of light reflectance or absorption along the length of the intestinemay be created and used for diagnostic or treatment purposes.

[0053] Additional features of the invention will appear from thefollowing description in which the preferred embodiments are set forthin detail in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE DRAWINGS

[0054]FIG. 1 illustrates the tracking system of the present inventionpositioned on a user.

[0055]FIG. 2 is a side partial cross-sectional view of a pod of thetracking system of FIG. 1.

[0056]FIGS. 3A and 3B are partial cross-sectional views of a firstembodiment of a capsule of the present invention with trackingcapabilities, used with the tracking system of the present invention.

[0057]FIG. 4 illustrates the electronic circuitry of the capsuleillustrated in FIG. 1.

[0058]FIG. 5 illustrates a schematic of the electronics of the recorderof the tracking system of the present invention.

[0059]FIG. 6 illustrates the pods such as the one illustrated in FIG. 2set up in an x, y, z Cartesian coordinate system.

[0060]FIG. 7 illustrates the location of a capsule on the x, y, zCartesian coordinate system of FIG. 6.

[0061] FIGS. 8A-G illustrate a timing diagram of signal emission andreception of an exemplary tracking system of the present invention.

[0062]FIG. 8A illustrates the emission of the RF reference signal.

[0063]FIG. 8B illustrates the emission of an ultrasound signal from thecapsule.

[0064]FIG. 8C illustrates the timing of the reception of the RFreference signal by the Pods.

[0065]FIG. 8D illustrates the timing of the reception of the ultrasonicsignal at the first Pod.

[0066]FIG. 8E illustrates the timing of the reception of the ultrasonicsignal at the second Pod.

[0067]FIG. 8F illustrates the timing of the reception of the ultrasonicsignal at the third Pod.

[0068]FIG. 8G illustrates the timing of the reception of the ultrasonicsignal at the fourth Pod.

[0069]FIG. 9 illustrates a partial cross-sectional view of a secondembodiment of a capsule of the present invention.

[0070]FIG. 10 illustrates a partial cross-sectional view of a thirdembodiment of a capsule of the present invention.

[0071]FIGS. 11A illustrates an example of the length of agastrointestinal system.

[0072]FIG. 11B illustrates an example of a map of pH as sensed inrelation to the linear position of a capsule along the length of thetract of FIG. 11A.

[0073]FIG. 11C illustrates an example of a map of pressure as sensed inrelation to the linear position of a capsule along the length of thetract of FIG. 11A.

[0074]FIG. 11D illustrates an example of a map of electrical activity assensed in relation to the linear position of a capsule along the lengthof the tract of FIG. 11A.

[0075]FIG. 11E illustrates an example of a map of sensed opticalcharacteristics in relation to the linear position of the capsule alongthe length of the tract of FIG. 11A.

[0076]FIG. 12 illustrates a partial cross-sectional view of a fourthembodiment of a capsule of the present invention.

[0077]FIG. 13 illustrates the electronic circuitry for the capsule ofFIG. 12, including ablation electronics.

[0078]FIG. 14 illustrates the electronic circuitry for an external powersource for the ablation function of the capsule of FIG. 12.

[0079]FIG. 15 is a partial cross-sectional view of a fifth embodiment ofa capsule of the present invention having a dissolvable encasingcontaining a deployable stimulation electrode.

[0080]FIG. 16 is a side elevational view of the capsule shown in FIG. 15with the encasing dissolved and the deployable stimulation electrodedeployed.

[0081]FIGS. 17A, 17B and 17C are graphs showing the programmable pacingparameters of the capsule shown in FIGS. 15 and 16.

[0082]FIG. 18 is a side elevational view of a sixth embodiment of thecapsule of the present invention.

[0083]FIG. 19 is a cut away view of a seventh embodiment of a capsule ofthe present invention and showing stimulation electrodes wrapped aboutthe capsule and encapsulated in a dissolvable encasing that is partiallycut away.

[0084]FIG. 20 is a partial cross sectional view of the embodiment ofFIG. 19 with the electrodes deployed.

[0085]FIG. 21 is a partial cross sectional view of an eighth embodimentof a capsule of the present invention with pressure sensingcapabilities.

[0086]FIG. 22 is an enlarged cross sectional view of a portion of thecapsule shown in FIG. 21.

[0087]FIG. 23 illustrates alternative electronic circuitry that may beused with the stimulation capsule.

[0088]FIG. 24 illustrates an alternative embodiment of a capsule fordetecting various optical characteristics from within the intestinaltract.

[0089]FIG. 25 is a graph illustrating the absorbtivity of hemoglobinwith respect to wavelength.

[0090]FIG. 26 is a graph illustrating relative differences inabsorbtivity of oxygenated versus deoxygenated hemoglobin at differentwavelengths.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0091] Referring to FIG. 1, there is illustrated a tracking system 160of the present invention positioned on a patient. The tracking system160 comprises an external recorder 105; four pods 101, 102, 103 and 104respectively, containing both acoustic and EM emitter/receivers; and acapsule 110 that is swallowable or otherwise positionable to move withinan intestinal tract. The recorder 105 is secured to the external abdomenof the patient. The pods 101, 102, 103 and 104 are adhered to the skinof the patient and have an acoustic transmitting/coupling material,e.g., a gel layer, interfacing between the skin of the patient and thepods 101, 102, 103, 104.

[0092] As illustrated in FIG. 2, the pod 101 comprises an outer plasticcasing 106 enclosing an acoustic transducer 107 a and an RF coil 108 a.The casing 106 has an interfacing wall 106 a for interfacing with theskin of a patient. An adhesive layer 109 is formed on a portion of theinterfacing wall 106 a, for adhering the pod 101 to the patient's skinwhile a remaining portion of the interfacing wall 106 a is exposed tothe patient's skin. The acoustic transducer 107 a is attached to thewall 106 a within the casing 106 adjacent the exposed portion of thewall 106 a in a manner that allows the acoustic or ultrasonic energy totransmit through the interfacing wall 106 a. On the opposite side of theacoustic transducer 107 a, an acoustic backing material 107 m isprovided that absorbs the acoustic energy transmitted in the directiontowards the backing material 107 m. Typically a gel or otheracoustically transmitting/coupling material is placed on the outside ofthe exposed portion of the interfacing wall 106 a. The output of theacoustic transducer 107 is coupled to wires 100 a that are coupled tothe recorder 105 through the wire conduit 100 extending out of thecasing 106. The RF coil 108 a is coupled through wires 100 b alsoextending through wire conduit 100 to recorder 105. Pods 102, 103, and104 are similarly constructed.

[0093] As illustrated in FIGS. 3A and 3B, a first embodiment of acapsule 110 comprises a liquid impermeable and airtight capsule body111. In general, the capsule of the present invention is sized so thatit is capable of being ingested for passage through the intestinaltract. For adult human use, a preferred embodiment of the capsule is tobe sized so that it has a length ranging from about 1.5 to 2.5 cm andhaving a diameter of about 8 mm or less. For children and larger andsmaller animals, the capsule can be appropriately sized. The capsulebody 111 contains and protects the enclosed circuitry from body fluidswhile passing through the intestinal tract. At least a portion of thecapsule body 111 is constructed of an ultrasound transmitting materialthat is compatible for use in the human body such as, for example, amedical grade plastic, e.g., polyethylene. A radiopaque marker 111 a isembedded in the plastic casing so that in the event it is necessary tolocate the device via an external imaging source, its location may beidentified. A dissolvable encasing (not shown) may surround the capsulebody 111. The encasing may be formed of a suitable dissolvable materialsuch as, for example, a soluble gelatin or enteric coating that isdissolvable in the body fluids contained in the stomach or intestinaltract. Such materials may be selectively dissolved based on the pHcondition so that the encasing dissolves after the capsule 110 haspassed through the highly acidic stomach and into the more neutral smallintestine. The capsule body 111 includes a generally hemispherical backend 131 and a generally hemispherical front end 132. The back end 131includes an inner end surface 131 a. The front end 132 includes an innerend surface 132 a. The overall conformation of the ingestible capsule110 is cylindrical in shape forming a substantially smooth outer capsulesurface.

[0094] The capsule 110 includes an RF coil 135 for transmitting andreceiving RF signals, and acoustic transducers 136 a, 136 b, and 136 clocated within the capsule body 111. The acoustic transducers 136 a and136 b are located against the inner end surfaces 132 a and 131 arespectively with an acoustic transmitting/coupling material filling anygap between the transducers 136 a and 136 b and the end surfaces 132 a,131 a in a manner so that the transducers can transmit acoustic,preferably ultrasonic waves through the capsule body 111 to thesurrounding tissue or material. Acoustic transducer 136 c is cylindricalin shape, extending around an inner circumference of the capsule. Anacoustic transmitting/coupling material similarly fills any gap betweenthe acoustic transducer 136 c and the inner wall of the capsule body111. The acoustic transducers 136 a-c are arranged in combination totransmit acoustic signals relatively omni-directionally.

[0095] The transducer 136 a comprises a piezoelectric crystal 137located between electrode plates 138 that when energized cause thecrystal to oscillate at an ultrasonic frequency (preferably between 100kHz and 5 MHz). An acoustic backing material 139, such as, oxideparticles in a flexible polymer, e.g., an epoxy matrix tungsten powder,is placed on the back of the transducer 136 a to absorb any acoustictransmissions in a direction opposite to the end surface 132 a. Theacoustic transducers 136 b and 136 c are constructed in a similar mannerto transducer 136 a and of similar materials. Other configurations of anacoustic transducer or transducers may be used to provide relativelyomni directional acoustic signal transmission. The RF coil 135 and theacoustic transducers 136 a, 136 b and 136 c are electrically coupled tothe electronics 113 which is powered by battery 114.

[0096] An elongate member 115 is affixed to the back end 131 of thecapsule body 111. First and second bipolar electrodes 116, 117 arelocated on the elongate member 115, the second bipolar electrode 117being electrically opposite of the first electrode 116. The elongatemember 115 is preferably formed of an elastically behaving material suchas a Ni—Ti alloy.

[0097] The capsule body 111 also includes a pH sensor 133 on the capsulebody 111. The pH sensor 133 is formed with dissimilar metals such as,e.g., silver chloride and antimony that sense differences in pH andconvert the sensed result into a calibrated electrical signal. The pHsensor is coupled to the electronics 113 by electrical conductors.

[0098] Referring now to FIG. 4, the electronic circuitry 113 of thecapsule 110 is illustrated. The electronic circuitry 113 is a chip thatincludes a number of optional connectors, and, as such, may be used in anumber of different diagnostic or therapeutic capsule configurations.The electronic circuitry 113 of the capsule 110 comprises, amicroprocessor or controller 122 for controlling the operations of theelectronic circuitry, an internal clock 121, and battery device 114 suchas a pair of lithium iodine batteries, for powering the variouscomponents of the circuit 113. As such, the controller 122 and batterydevice 114 are coupled to each of the major components of the circuit aswould be known to one of ordinary skill in the art.

[0099] The controller 122 is coupled to ROM 123, which contains theprogram instructions for the controller 122 and any other permanentlystored information that allows the microprocessor/controller 122 tooperate. The controller 122 addresses memory in a location in ROM 123through address bus 123 a and the ROM 123 provides the stored programinstruction to the controller 122 via data bus 123 b.

[0100] The electrode plates 138 of the acoustic transducer 136 a arepowered through oscillator 137 a controlled by the controller 122 toproduce a desired acoustic wave output. Similarly, electrode plates ofacoustic transducers 136 b and 136 c are powered through oscillators 137b and 137 c, respectively, controlled by the controller 122. Thecontroller 122 controls the RF coil 135 that acts either to deliver anRF tracking signal or as a telemetry device for communicating data tothe recorder 105. The RF coil 135 delivers signals to or receivessignals from the RF coils 108 a-d (FIG. 5) in the pods 101, 102, 103,and 104. For tracking purposes, controller 122 will respectively, atfixed time intervals, order the transmission of an RF signal and anacoustic signal using the RF coil 135 and at least one of acoustictransducers 136 a-136 c. The controller's commands will incorporate apreset time interval between the RF signal transmission and acousticsignal initiation. Such time interval (which could be zero) will befactored in at the recorder 105 to determine acoustic wave transmissiontime. In the preferred embodiment, the capsule's acoustic transducers136 a-136 c transmit the acoustic signals immediately, or a defined timeafter the RF reference signal. The acoustic transducer 136 a will emit afirst signal a predetermined time after the RF signal, the second andthird acoustic transducers 136 b and 136 c will emit second and thirdsignals respectively at predetermined times after the RF signal andsufficiently spaced in time from the other signals so that the acousticsignals may be differentiated. Alternatively, the second and thirdacoustic signal may be referenced from second and third differentiatedRF signals.

[0101] When the RF coil 135 is receiving an external telemetry signal,the buffered oscillator 119 is disabled. Telemetry signals received onRF coil 135 are detected in a detector circuit 119 a and communicated tomicroprocessor 122. The detector circuit 119 a is preferably selectedbased on the modulation used for the telemetry signals.

[0102] One or more sensors, e.g., 127 a (pressure), 127 b (pH), 127 c(optical), 127 d (temperature), and 116, 117 (electrodes) may be coupledto controller 122 through A/D converters (with amplifiers) 126 a, 126 b,126 c, 126 d, 126 e which convert a representative analog electricalsignal into a digital signal. Suitable sensors of these types aregenerally known in the art and may be located within, on, or external tothe capsule body 111. The electrodes 116, 117 used to deliver thestimulation are also used to sense electrical activity or impedance asdescribed in further detail herein.

[0103] The controller 122 is coupled to RAM 120 via an address bus 120 afor addressing a location in RAM 120 and a bi-directional data bus 120 bfor delivering information to and from RAM 120. The RAM 120 includesevent memory 124 that temporarily stores data recorded by sensors 127a-127 d and electrodes 116, 117. RAM 120 also includes a programmablememory 125 which may be programmed, for example, via telemetry while thecapsule 110 is within the intestinal tract, to provide treatmentprotocols. The data stored in the event memory 124 may be sent toexternal coils 108 a-d (FIG. 5) intermittently as data bursts viatelemetry through the RF coil 135, as opposed to continuously in orderto save battery power. The data stored in the programmable memory 125may include specifications for the electrical stimulation operatingmodes (e.g. waveform, type of stimulation: for pacing, inducingcontraction or other type) and various procedure parameters (e.g., whento deliver a drug or electrical stimulation). Such programming may bedone in response to sensed information or it may be done automaticallyby an external controller or as desired by a treating physician, etc.

[0104] Controller 122 is coupled to a buffered oscillator 119 thatprovides an RF signal to be emitted from the RF coil 135. The RF signalis preferably at about 100 kHz to about 5 MHz so that the signal isefficiently transmitted through tissue. The controller 122 controls theoscillator 119 and provides data for example, various sensed data suchas pressure, pH, impedance, electrical activity, etc., to be modulatedwith the RF signal to be delivered through RF coil 135. The controller122 may also be coupled through stimulation driver 118 and couplingcapacitors 116 a, 117 a to bipolar stimulating electrodes 116, 117,respectively. Electrical stimulation may be provided in a manner similarto that described herein with reference to the stimulating electrodes 16a-c, 17 a-b, 56, 57, 66, 67, 86, and 87 of FIGS. 15-22. The stimulationmodes and parameters can be preprogrammed or set by an external devicethat telemetrically communicates the parameters.

[0105] The battery 114 has its output supplied to a DC-to-DC converter130 to provide a higher voltage, which is utilized for electricalstimulation pulses. The DC-to-DC converter 130 is conventional andprovides an output voltage of 15 to 20 volts. Further the circuit 113may include one or more drivers 128 a, 128 b, 128 c, 128 d that drivevarious devices, for example, diagnostic or therapeuticelectromechanical devices, such as controlling valves, solenoids, etc,for, e.g., drug delivery, biopsy, content sampling, or a marker release,etc. The controller 122 provides a signal to a driver 128 a-128 d basedon a preset program in ROM 123, on sensed parameters stored in RAM 120,and/or on a telemetrically received signal from the recorder 105 or RFcoils 108 a-d in the pods, 101-104. The circuit may also include astepping driver 129 coupled to a stepper motor for example for rotatingan imaging device (e.g., diagnostic ultrasonic device) or actuating abiopsy device, etc.

[0106] Referring now to FIG. 5, a schematic of the electronic circuitry140 of the recorder 105 of the present invention is illustrated. Theelectronic circuitry 140 of the recorder 105 comprises: a microprocessoror controller 142 for controlling the operations of the electroniccircuitry, an internal clock 141, and power source such as a battery 147for powering the various components of the circuit 140. The controller142 and battery device 147 are coupled to each of the major componentsof the circuit in a manner known to one of ordinary skill in the art.

[0107] The electronic circuitry 140 is coupled to the pods 101, 102, 103and 104, which respectively include RF coil sensors 108 a-d and acoustictransducers 107 a-d that send and receive signals to and from thecapsule 110. The details of the coupling of the transducer 107 a and 108a are illustrated in FIG. 5. The transducers 107 b-d and coils 108 b-dare coupled in a similar manner not shown. The output of the RF coil 108a is coupled through a demodulator 155 to the controller 142. Thedemodulator 155 demodulates the information carried by the RF signalreceived by the RF coil 108 a. Such information may include, forexample, telemetrically delivered sensed data. Also, the RF coil 108 amay emit an RF reference signal. The controller 142 controls the outputof the RF coil 108 a, which communicates with the capsule 110. Thecontroller 142 is coupled to an oscillator 156 that provides a carriersignal, preferably having a characteristic frequency in the range of 100kHz to 5 MHz so that it may be efficiently transmitted through tissue tothe capsule. The controller 142 provides data to be modulated with theRF signal, for example, commands to the capsule 110 to providetreatment, treatment parameters, etc. The controller 142 controls theoutput of acoustic transducer 107 a through oscillator 157, whichprovides the oscillating frequency to the transducer when the pod ispinging another pod, i.e., when the pods are sending signals tocalibrate the pods and identify their locations on the coordinatesystem. The controller 142 also receives the representative acousticsignal from the transducer 107 a through automatic gain control device158 which brings the voltage or current levels within a predefinedrange, and through filter 159.

[0108] The controller 142 is further coupled to ROM 143, which containsthe program instructions for the controller 142 and any otherpermanently stored information that allows the microprocessor/controller142 to operate. The controller 142 addresses memory in ROM 143 viaaddress bus 143 a and the ROM 143 provides the stored programinstruction to the controller 142 via data bus 143 b.

[0109] The controller 142 is coupled to RAM 144 via address bus 144 aand bi-directional data bus 144 b. The RAM 144 comprises event memory145 that temporarily stores data sent via telemetry from the capsule 110to the RF coils 108 a-d in the pods 101-104 until the data is downloadedonto a computer using external data port 150. For tracking purposes, theRAM 144 is also used to store the data concerning lag times between theRF signal and acoustic signals received by transducers 107 a-d, and RFcoils 108 a-d in the pods 101-104. The RAM 144 also comprises aprogrammable memory 146, which is used to specify operation modes (e.g.waveform, type of stimulation: for pacing, inducing contraction or othertype) and various procedure parameters that may be transmitted to thecapsule 110 through RF coils 108 a-d via telemetry. The recorder 105also includes a display 151 to show recorded data, sensed parameters,treatment parameters, and status of device (e.g., capsule position,battery charge status, etc.). The recorder 105 also includes a datainput device 152 such as a keyboard, pad or input screen for inputtingnew parameters, programming the capsule, changing the treatment scheme,viewing various data or turning the device on or off. The input iscoupled through a buffer 154 to the controller 142. The controller 142is coupled to a speaker 153 for providing audible information such as analert.

[0110] In FIGS. 6 and 7, the pods 101,102,103, and 104 are set up in anCartesian (x,y,z) coordinate system. The origin of the coordinate systemis defined as the location of pod 101. The y-axis is defined as the linethat passes through pod 101 and pod 102. The x-y plane is defined as theplane that intersects pods 101, 102 and 103. The z-axis is perpendicularto the x-y plane. Pod 104 is located off of the x-y plane. Thus, thecoordinates of the pods in this defined coordinate system are:

[0111] Pod 101: (0, 0, 0)

[0112] Pod 102: (0, y₂, 0)

[0113] Pod 103: (x₃, y₃, 0)

[0114] Pod 104: (x₄, y₄, z₄)

[0115] where the pod coordinates y₂, x₃, y₃, x₄, y₄, and z₄ areinitially unknown.

[0116] Once the pods are placed as illustrated in FIG. 1, thecoordinates of the pods are initially determined in the followingmanner. As illustrated in FIG. 6, the distances d₁₂, d₁₃, d₁₄, d₂₃, d₂₄,and d₃₄ represent the distances between pods 101 and 102, 101 and 103,101 and 104, 102 and 103, 102 and 104, and 103 and 104, respectively.The pods, which can both emit and receive electromagnetic and acoustic(including ultrasound) signals, will sense time-lags between the RF andacoustic signals sent between the pods along the distances d₁₂, d₁₃,d₁₄, d₂₃, d₂₄, and d₃₄, i.e., the pods will ping each other. The podscommunicate with a processor located in the recorder that calculates thedistance and determines the coordinates. The time-lags are multiplied bythe velocity of sound to calculate the distances (d₁₂, d₁₃, d₁₄, d₂₃,d₂₄, and d₃₄) between the pods.

[0117] Under Pythagoras' Theorem the following six equations relate thecoordinates of the pods and the distances between them:

(x ₂-x ₁)²+(y ₂-y ₁)²+(z ₂-z ₁)² =d ₁₂ ²  (1)

(x ₃-x ₁)²+(y ₃-y ₁)²+(z ₃-z ₁)² =d ₁₃ ²  (2)

(x ₄-x ₁)²+(y ₄-y ₁)²+(z ₄-z ₁)² =d ₁₄ ²  (3)

(x ₃-x ₂)²+(y ₃-y ₂)²+(z ₃-z ₂)² =d ₂₃ ²  (4)

(x ₄-x ₂)²+(y ₄-y ₂)²+(z ₄-z ₂)² =d ₂₄ ²  (5)

(x ₄-x ₃)²+(y ₄-y ₃)²+(z ₄-z ₃)² =d ₃₄ ²  (6)

[0118] The pod coordinates x₁, y₁, z₁, x₂, z₂, and z₃ are defined ashaving the value of 0. Thus, plugging in the known pod coordinates, theequations can be rewritten as:

y ₂ ² =d ₁₂ ²  (1′)

x ₃ ² +y ₃ ² =d ₁₃ ²  (2′)

x ₄ ² +y ₄ ² +z ₄ ² =d ₁₄ ²  (3′)

x ₃ ²+(y ₃ −y ₂)² =d ₂₃ ²  (4′)

x ₄ ²+(y ₄ −y ₂)² +z ₄ ² =d ₂₄ ²  (5′)

(x ₄ −x ₃)²+(y ₄ −y ₃)² +z ₄ ² =d ₃₄ ²  (6′)

[0119] With these six equations, and the determined distances, d₁₂, d₁₃,d₁₄, d₂₃, d₂₄, and d₃₄, the six pod coordinates, y₂, x₃, y₃, x₄, y₄, andz₄ may be solved. Single solutions for all the coordinates may beobtained by setting the following position restrictions: y₂>0; x₃>0; andz₄>0. In other words, pod 101 should be placed on the right side of theuser, pod 102 on the left side, pod 103 on the lower abdomen, and pod104 on the upper abdomen as illustrated in FIG. 1.

[0120] The determination of the solutions for the six pod coordinatesy₂, x₃, y₃, x₄, y₄, and z₄ are described below:

[0121] Equation (1′) gives:

y ₂ =d ₁₂  (1″)

[0122] Plugging (1″) into (4′) and subtracting (4′) from (2′) gives:

y ₃=(d ₁₂ ² +d ₁₃ ² −d ₂₃ ²)/(2d ₁₂)  (2″)

[0123] Plugging (2″) back into (2′) gives:

x ₃=(d ₁₃ ² −y ₃ ²)^(0.5)  (3″)

[0124] where y₃ has been solved above.

[0125] Plugging (1′) into (5′) and then subtracting (5′) from (3′)gives:

y ₄=(d ₁₂ ² +d ₁₄ ² −d ₂₄ ²)/(2d ₁₂)  (4″)

[0126] Subtracting (6′) from (3′) gives:

x ₄=(d ₁₄ ² −d ₃₄ ² +x ₃ ² +y ₃ ²−2y ₃ y ₄)/(2x ₃)  (5″)

[0127] where x₃, y₃ and y₄ have been solved above.

[0128] Plugging (4″) and (5″) into (3′) gives:

z ₄=(d ₁₄ ² −x ₄ ² −y ₄ ²)^(0.5)  (6″)

[0129] where x₄ and y₄ have been solved above.

[0130] The pod coordinates are determined whenever the pods arere-positioned. The pod coordinates may also be re-established at regularintervals to account for movement and thus relative change in podposition.

[0131] As illustrated in FIGS. 7 and 8A-G, using the coordinates of thepods, the location of the capsule in space may be determined as follows.The range-finding capability of the pods measure the distances betweenthe capsule 110 and each pod. As illustrated in FIGS. 8A-B, the capsule110 emits an RF signal 205 and a sychronized ultrasonic signal 206 thatis emitted a predetermined time interval after the RF signal 205 isemitted. In the preferred embodiment the ultrasound signal 206 isemitted immediately following the RF signal 205. In this drawing, forillustrative purposes the signal emitted from transducer 136 a isillustrated. Second and third acoustic signals emitted from the secondand third transducers 136 b and 136 c would be similar to the signalemitted from transducer 136 a except that they preferably emitted afterthe first signal 206 and at predetermined time intervals from the RFsignal 205. The signals from the additional acoustic transducers 136 band 136 c may also alternatively have different waveforms as that of thefirst signal 206. FIG. 8C illustrates the timing of when the RF signal205 is received at the pods. FIGS. 8 D-G illustrate the timing of whenthe ultrasound signal 206 is respectively received at pods 101, 102,103, and 104. Because the RF signal 205 travels at the speed of light,it is received by the pods 101, 102, 103 and 104 at a relativelynegligible time delay in comparison to the ultrasonic signal whichtravels generally at about 1540 meters per second in human tissue. Thedistances c₁, c₂, c₃, and c₄ represent the distances between the capsuleand pods 101, 102, 103, and 104, respectively. The pods 101, 102, 103and 104 receive the ultrasound signal 206 transmitted from the capsule110 at varying times depending on the distances c₁, c₂, c₃, and c₄respectively. Such time lags may be represented as illustrated, forexample, in FIG. 8 as t₁, t₂, t₃, and t₄ corresponding to distances c₁,c₂, c₃, and c₄, respectively. The time-lags will then be multiplied bythe velocity of sound to calculate the distances (c₁, c₂, c₃, and c₄)between the capsule 110 and each pod.

[0132] Using Pythagoras' Theorem the following equations relate thecoordinates of the capsule (x_(n), y_(n), z_(n)) and pods, and thedistance between them:

(x _(n)-x ₁)²+(y _(n)-y ₁)²+(z _(n)-z ₁)² =c ₁ ²  (7)

(x _(n)-x ₂)²+(y _(n)-y ₂)²+(z _(n)-z ₂)² =c ₂ ²  (8)

(x _(n)-x ₃)²+(y _(n)-y ₃)²+(z _(n)-z ₃)² =c ₃ ²  (9)

(x _(n)-x ₄)²+(y _(n)-y ₄)²+(z _(n)-z ₄)² =c ₄ ²  (10)

[0133] These four equations may be solved to obtain a single solutionfor the three coordinates of the capsule, x_(n), y_(n), and z_(n).

[0134] According to one embodiment, a three-dimensional orfour-dimensional map of the capsule's trip through the intestinal systemcan be generated by measuring the capsule's coordinates at fixed timeintervals.

[0135] Alternatively, linear travel distance measurements can be made byusing Pythagoras' Theorem. Incremental linear distances can becalculated and then summed to obtain a total linear travel distance (L):

L= _(o) ^(m)[(x _(n+1) −x _(n))²+(y _(n+1) −y _(n))²+(z _(n+1) −z_(n))²]^(1/2),

[0136] where m is equal to the number of incremental distances and where(x_(n), y_(n), z_(n)) and (x_(n+1),y_(n+1),z_(n+1)) are consecutivecapsule coordinate measurements used to measure incremental lineardistances traveled. In this manner a linear map of the capsule'sposition along the intestinal tract may be obtained. Such a map showsthe position of the capsule along the tract independent of actual 3Dspatial orientation. Thus, errors based on intestinal shifting,peristaltic motion, patient positioning, and change in pod location arereduced without requiring additional sensed information. Retrogradeperistaltic motion can occur in the small intestine. An algorithm may beused to cancel out any backtracking travel measurements when calculatingthe linear distance traveled by the capsule. As described below using anadditional acoustic transducer, (e.g., located on the opposite end ofthe capsule) and obtaining the same positional information may provideinformation on capsule orientation and direction of capsule movement.Preferably, the additional transducer will deliver a signal at timeintervals between the acoustic signals of the first transducer. Thesignals from the additional transducer may have a different waveform todifferentiate the signal from signals corresponding to the firsttransducer. The orientation information may provide additionalinformation that is used to cancel out retrograde capsule movement.

[0137] Referring to FIGS. 11A-D, an example of a linear map of anintestinal tract and corresponding maps of sensed information areillustrated. FIG. 11A illustrates an example of a linear map of agastrointestinal tract. FIG. 11B illustrates an example of a map of pHsensed by a capsule in relation to its linear position along the lengthof the tract of FIG. 11A. FIG. 11C illustrates an example of a map ofpressure sensed by a capsule in relation to its linear position alongthe length of the tract of FIG. 11A. FIG. 11D illustrates an example ofa map of electrical activity sensed by a capsule in relation to itslinear position along the length of the tract of FIG. 11A. These mapsmay be plotted from sensed information on a display screen in theillustrated format or as otherwise may be desirable by a user.

[0138] The parameters shown in the maps in FIGS. 11B-D may be determinedby a capsule having sensing capabilities. As the capsule passes throughthe intestinal tract and its location along the length is determined,other parameters relating to the condition of the intestinal tract maybe sensed periodically or continuously. The sensed conditions may besent via telemetry to one or more pod receivers. This may occurindependently from the time of the RF reference signal transmission andthe acoustic signal transmission so that the telemetry signal isindependent of the coordinate determining RF reference signal. Thesensed information is mapped along the length of the intestine by thetracking system as described above. A linear map of sensed informationis overlaid on the linear map of the intestine so that unusual parametervalues, or areas to be treated may be determined. Upon a second pass ofa capsule, the area or portion of the tract to be treated may be locatedalong the length of the linear map created from the first capsule pass.The second capsule uses a similar method to determine its position alongthe length of the tract and its linear travel position is compared tothe linear travel position of the first capsule. Thus, when the capsulehas traveled the appropriate position along the tract, the segment ofthe tract may then be treated. Treatment may be triggered by atelemetric signal sent to the capsule when the recorder and externalcontroller have calculated the appropriate linear position.

[0139] Referring now to FIG. 9, there is illustrated a second embodimentof a treatment capsule of the present invention. Capsule 170 comprises acapsule body 171 including an electronic circuit 113 and battery 174coupled to the electronic circuit 113. An RF coil 175 and acoustictransducers 176 a-c operate in a similar manner as RF coil 135 andtransducers 136 a-c described herein. The capsule further comprises acompressed gas source 165 and an inflatable balloon 167 externally fixedto the capsule body 171. The gas source 165 is in fluid communicationwith a valve 166 that opens into a chamber 168 in the balloon 167. Thechamber 168 of the balloon 167 further is in fluid communication with avalve 169 that opens to a gas exit port 172 that is in fluidcommunication with the intestinal tract. The valves are coupled throughdrivers 128 a, 128 b in electronic circuit 113. The operation of thevalves 166, 169 is controlled by the controller 122 in the electroniccircuit. 113. In use, the capsule is delivered after a diagnosticcapsule using an optical sensor has been passed through the intestinaltract to obtain a map of optically sensed parameters along the length ofthe tract. After a blockage site along the length has been determined,the capsule 170 is ingested. Using the RF coil 175 and acoustictransducers 176 a-c of the tracking system described above, the trackingsystem identifies when the capsule 170 has reached the blocked site. Thetracking system sends a telemetric control signal to the RF coil 175that instructs the controller 122 to inflate the balloon 167. Thecontroller activates valve 166 through driver 128 a which opens to allowcompressed gas from the gas source 165 to fill the chamber 168 of theballoon. The inflation of the balloon 167 expands the intestinal wall atthe site of the balloon 167 to open the blockage. The controller 122then opens the valve 169 through driver 128 b to allow the gas to escapefrom the chamber 168 through the gas exit port 172 and into theintestinal tract. The controller may release the gas upon an externaltelemetrically delivered command that is initiated by, for example, aphysician who is observing the capsule and balloon under fluoroscopy, todetermine if and when a blockage has been opened. Alternatively, theballoon may be preprogrammed to expand for a predetermined amount oftime. The expandable member may be used for a variety of diagnostic ortreatment purposes, for example, pressure sensing, opening partialblockages, measuring the openings of partially blocked or constrictedareas, providing hemostasis, delivering therapeutic substances that arecoated on the balloon 167, or affixing a capsule in an identifiedlocation to mark the location in the intestine. An expandable supportmember such as a stent may be provided on the balloon for placementwithin a stricture upon expansion of the balloon. Alternatively, thecapsule may be provided with a self-expanding support structure such asa self-expanding stent.

[0140]FIG. 10 illustrates a third embodiment of a treatment capsule ofthe present invention. Capsule 180 comprises a capsule body 181including an electronic circuit 113 and battery 184 coupled to theelectronic circuit 113. An RF coil 185 and acoustic transducers 186 a-coperate in a similar manner as RF coil 135 and transducer 136 a-cdescribed herein. The capsule further comprises a pump 187 filled with adye such as, e.g., fluorescein or methylene blue to provide a surgeonwith identification of a site for surgery. Such marker may include, forexample a radiopaque marker that may be located with an active x-raysystem during a procedure, a radioactive material that may beinterrogated by a passive system, a fluorescing compound that is used toidentify the location, or a dye that stains through the wall of theintestine. The compounds may assist a surgeon in a laparoscopic or openprocedure where such imaging systems are used during the procedure orwhere visualization, e.g., of a dye or stain is possible. The pump iscoupled to a valve 189 by a conduit 188. The pump 187 and the valve 189are controlled by the controller 122 in the electronic circuitry 113through drivers 128 c and 128 d. In use, the capsule 180 is deliveredafter a diagnostic capsule having a diagnostic sensor has been passedthrough the intestinal tract to obtain a map of sensed parameters alongthe length of the tract. After a site along the length of the tract hasbeen identified for surgical intervention, the capsule 180 is ingested.Using the RF coil 185 and acoustic transducers 186 a-c of the trackingsystem described above, the tracking system identifies when the capsule180 has reached the identified site. The tracking system sends atelemetric control signal to the RF coil 185 that instructs thecontroller 122 to activate the pump 187. The controller activates thepump 187 through driver 128 c. The controller also activates valve 189through driver 128 d which opens to allow dye from the pump 187 to exitthe pump through conduit 188 and valve 189 and be sprayed onto theadjacent intestinal wall. The dye thus marks a location for surgicalintervention.

[0141] The capsule 180 may also be used to release a gas into theintestinal tract at a given location where e.g. a blockage or otheranatomical feature is believed to exist. Using fluoroscopy, the anatomymay be observed. Similarly, using a capsule such as capsule 180, a fluidsuch as a radiopaque fluid may be released near a contriction or otherarea to be imaged where pump 187 pumps the fluid into the intestinaltract through a conduit 188 and valve 189.

[0142] FIGS. 12-14 illustrate a fourth embodiment of a treatment capsuleof the present invention. Capsule 210 comprises a capsule body 211including an electrocautery ablation circuit 213, an electronic circuit113, and a battery 214 coupled to the electronic circuit 113. Thecapsule 210 also comprises an elongate member 225 with a larger areareturn electrode 227 located thereon. The elongate member 225 andelectrodes 226, 227 are constructed in a manner similar to elongatemember 15 and electrodes 16 a, 16 b, and 16 c described with respect toFIGS. 15-16 herein. A small area ablation electrode 226 is located onthe capsule body 211, preferably in the form of a ring. A thermocouplesensor 127 d is located on the capsule body 211 immediately adjacent tothe ablation electrode 226 so that the sensor can sense the temperatureof tissue that is being treated by the ablation electrode 226 andprovide a feedback loop to an external controller 142 that regulates thepower delivered to the ablation electrode 226. An RF coil 215 andacoustic transducers 216 a-c operate in a similar manner as RF coil 135and transducers 136 a-c described herein. The RF coil 215 has afrequency response of about 1 MHz.

[0143] As illustrated in FIG. 13, the ablation electronics include, anablation coil 221, electrodes 226, 227, and an ablation circuit 213including a capacitor 222. The ablation coil 221 that is tuned to afrequency of about 250 kHz, thus the coils 215 and 221 receive differentfrequencies, enabling them to distinguish between a telemetry signal andan ablation power signal. An external variable power generator 230 (FIG.14) supplies an RF signal at 250 kHz through power transmitter coil 231.The ablation signal received by the ablation coil 221 and paralellcapacitor 222 (which together form a tuned circuit to separate theablation signal from the telemetry signal) is then delivered toelectrodes 226, 227. The ablation electrode 226 has a considerablysmaller area than the return electrode 227 so that the current densityis greater at the ablation electrode 226 where the ablation current isto be focused on the adjacent tissue. The thermocouple sensor 127 dprovides an electrical signal representative of the temperature of theadjacent tissue, through the A/D converter 126 d of the capsule circuit113. The signal is converted to a digital signal that is provided to thecontroller 122 of the circuit 113. The signal is telemetricallydelivered to the controller 142 of the recorder 105 in a manner asdescribed herein.

[0144] As illustrated in FIG. 14, the power is controlled by thecontroller 142 of the recorder 105 which is coupled to the powergenerator 230 by way of connector 233. The controller 142 in therecorder electronics 140 will regulate the power output to the ablationelectronics based on feedback information as sensed by the thermocouple127 d on the capsule body 211 and delivered via telemetry from thecapsule RF coil 215. The regulation of the power is significant in thisembodiment as the RF ablation signal strength may vary with distancefrom the capsule, the type of the tissue being treated, the impedance ofthe tissue being treated. Thus, the temperature feedback loop isintended to prevent over or under heating of the tissue. In addition,the treatment is initiated by a user by activating a switch 234 coupledto the power generator 230.

[0145] In use, the tracking system is used in a manner as describedabove. A location to be treated along the length of the intestinal tractis first identified by a first capsule passing through the tract.Preferably the capsule will have an optical, chemical or other means fordetermining a location where bleeding is occuring. This location isidentified in a subsequent pass of the ablation capsule 210 and the userturns the ablation power on when the appropriate location is identifiedto ablate or cauterize the tissue that is bleeding. In a variation ofthe embodiment, a site where bleeding is present may be treated using asubsequently passed capsule having a balloon tamponade, i.e. aninflatable member that uses compression and/or a thrombogenic substancecoated on the inflatable member to help cause hemostasis. A capsuleembodiment having an inflatable member is described herein withreference to FIGS. 21 and 22.

[0146] FIGS. 15-16 illustrate a fifth embodiment of the capsule of thepresent invention. The capsule 10 comprises a treatment and sensingdevice that may be used with the tracking system. The capsule 10 is usedto sense electrical parameters of the intestinal wall and/or to treatthe intestinal tract by electrically stimulating the intestinal wall.The capsule 10 comprises a liquid impermeable and airtight capsule body11. The capsule body 11 contains electronic circuitry 113, battery 114,RF coil 135 and acoustic transducers 136 a-c as described above withreference to FIGS. 3A and 3B. The capsule body 11 protects the enclosedcircuitry from body fluids while passing through the intestinal tract.The capsule body 11 is formed of a material that is compatible for usein the human body, for example, a medical grade plastic or polymer.

[0147] An elongate member 15 is affixed to an end of the capsule body11. Electrodes 16 a, 16 b and 16 c are located on the elongate member15. Two second, larger area electrodes 17 a and 17 b extend around thewidth of the capsule body 11. Electrodes 16 a-c may be selected in anumber of combinations to form electrode pairs to deliver stimulation tothe intestinal wall (or alternatively to sense electrical activity ofthe intestinal wall). Additionally, one or more of electrodes 17 aand/or 17 b may be utilized to work with one or more of electrodes 16a-16 c where current density will be concentrated at the smallerelectrode(s) 16 a, 16 b, and/or 16 c. The capsule electronics mayinclude logic to select which electrodes should deliver stimulationpulses for optimal stimulation. The electronics may similarly controlwhich electrodes may be used to sense electrical activity of theintestinal wall. Alternatively, an external processing unit maydetermine optimal electrode selection that is communicated to thecapsule by a telemetry command signal.

[0148] In one preferred embodiment, the capsule 11 may be used forstimulation and subsequent measurement of electrical parameters. Thisfunction may be used for diagnostic purposes, for example, to determineif the intestinal wall is properly conducting electrical pulses or ifthe wall at a particular location is an electrically hypo-active or“dead” area. In a preferred embodiment, the capsule electrodes areelectrically configured so that a plurality of adjacent electrode pairscan be used where a first pair stimulates the intestinal wall at a firstlocation and the second pair then detects signals at a second locationthat are propagated from the original stimulation signal. Accordingly,in a variation of one embodiment, to determine if the intestinal wall iselectrically abnormal, e.g., is electrically hypo-active, electrodes 17a and 17 b are used to deliver a stimulation signal and an electrodepair formed from at least two of electrodes 16 a-c are used to senseresulting signals propagated in an orad direction. In a variation ofanother embodiment, signal propagation in the aborad direction, i.e.,from the back of the capsule to the front assuming the front of thecapsule is oriented in a direction away from the mouth is determinedusing an electrode pair formed from at least two of electrodes 16 a-care used to deliver a stimulation signal and electrodes 17 a and 17 bsense resulting propagated signals.

[0149] As illustrated in FIG. 15, a dissolvable encasing 12 surroundsthe elongate member 15, the electrodes 16 a-c, and at least a portion ofthe capsule body 11. When encapsulated by the encasing 12, the elongatemember 15 is in a coiled or compressed position.

[0150] The encasing 12 is formed of a suitable dissolvable material suchas, for example, a soluble gelatin or enteric coating that isdissolvable in the body fluids contained in the intestinal tract. Suchmaterials may be selectively dissolved based on the pH condition so thatthe encasing 12 dissolves after the capsule 10 has passed through thehighly acidic stomach and into the more neutral small intestine.

[0151] The elongate member 15 is preferably formed of a material thathas elastic properties such as a Ni—Ti alloy, which permits it to becompressed into the initial configuration and to release into itselongate state when the encasing 12 has dissolved. As shown in FIG. 16,the elongate member 15 extends into its elongate form when the encasing12 has dissolved.

[0152] The capsule body 11 is provided with a front portion 11 a and aback portion 11 b of reduced diameter. The encasing 12 is bonded to theback portion 11 b by suitable means such as an adhesive. The diameter ofthe back portion 11 b is reduced by a sufficient amount so that thethickness of the encasing 12 forms a substantially smooth outer capsulesurface in conjunction with the outer surface of the front portion 11 aof the capsule body 11. The overall conformation of the ingestiblecapsule 11 is cylindrical in shape having a generally hemispherical endsurface 23 on the front portion 11 a and a generally hemispherical endsurface 24 on the back portion 11 b. Dissolvable encasing 12 also has agenerally hemispherical end surface 12 a.

[0153] It is desirable that the elongate flexible member 15 have anextremity which has a curved configuration so as to ensure that thestimulation electrodes 16 a-c are maintained in close proximity to thewall of the intestinal tract as the capsule 10 moves through theintestinal tract as hereinafter described. The electrode 17 is formed ofa conducting layer of a suitable metal such as gold deposited on thesurface of the capsule body 11. Alternatively, the additional electrodes16 b and 16 c may be carried by additional elongate members constructedand secured to the capsule body 11 in a similar manner as elongatemember 15.

[0154] The electronic circuitry 113 shown in FIG. 4 is capable ofproducing various types of programmable waveforms. FIGS. 17A and 17Billustrate examples of stimulation waveforms that may be used instimulating the smooth muscle layer of the intestinal tract. FIG. 17Aillustrates a waveform design for stimulating the intestinal tract. In apreferred embodiment, the waveform 300 has a pulse amplitude of between1 and 30 mA, a pulse width of between 0.5 and 300 ms, and a frequency ofabout between 8 to 12 cycles per minute (this corresponds to arepetition period of between 5 to 7.5 seconds). FIG. 17B illustrates analternative waveform design for stimulating the intestinal tract. Thewaveform 400 utilizes bursts of pulses rather than a single pulse. Theburst repetition rate is selected, preferably, to be between about 8 to12 cycles per minute (this corresponds to a burst repetition period ofbetween 5 to 7.5 seconds). The duration of a pulse in this example isbetween about 300 μs and 20 ms, and has an amplitude of about 1-30 mA.The frequency of the burst pulses during a burst period are about 50 to100 Hz corresponding to a pulse repetition period of 10 to 20 ms. Theburst duration can vary from about 0.6 ms to 1 second. As is well knownto those skilled in the art, there are many different types ofelectrical stimulation programs and strategies which can be utilized forproviding electrical stimulation parameters through the circuitry 113,the principal focus being providing electrically stimulating parametersfor the intestinal tract, preferably the small intestine.

[0155]FIG. 18 illustrates a sixth embodiment of a capsule of the presentinvention. Stimulation capsule 50 is generally constructed in a similarmanner as capsule 110. Capsule 50 comprises first bipolar electrode 56and a second, electrically opposite bipolar electrode 57 on a capsulebody 51 in longitudinally spaced apart positions. The electrodes 56, 57are connected by conductors to the electronics 113 within the capsulebody 51. According to this embodiment, various electrical stimulationparameters, including those described herein, may be used.

[0156] A seventh embodiment of the capsule is shown in FIGS. 19 and 20.Capsule 60 comprises a stimulation electrode deployment mechanismconsisting of a loop 76 formed of an elastic material wrapped about thecapsule body 61. Bipolar stimulating electrodes 66 and 67 are carried bythe loop 76 and are connected to the electronic circuitry 113 in thecapsule body 61 by conductors (not shown) extending through the hollowtubular member forming the loop 76. As shown in FIG. 19, a dissolvableencasing 62 is provided over the capsule body 61. This encasing 62 canbe formed of the same material as the encasing 12 in the embodimentshown in FIG. 15. When encasing 62 is dissolved, the loop 76 will expandto the ovoid looped configuration shown in FIG. 20, bringing thestimulation electrodes 66 and 67 into contact with the wall of theintestinal tract as the capsule 60 travels through the intestinal tract.The loop 76 allows the electrodes 66, 67 to be positioned behind (oradto) the capsule 60 regardless of its orientation in the intestinaltract. As the capsule 60 moves through the intestinal tract the loop 76will be in contact with the wall of the tract. The friction forces ofthe loop 76 dragging along the wall will cause the loop 76 to shift suchthat the electrodes 66, 67 are generally behind (orad to) the capsule.In this regard, a contraction stimulated by the electrodes 66, 67 willtend to result in forward (aborad) movement of the capsule as thestimulated contraction propagates along the intestinal tract.

[0157]FIGS. 21 and 22 illustrate an eighth embodiment of a capsule ofthe present invention. Capsule 80 includes an expandable member. InFIGS. 21 and 22, an inflatable member with pressure sensing capabilitiesis illustrated. Electronic circuitry 113 is located in the capsule body81. A pressure transducer 127 a, also located in the capsule body 81 iscoupled to circuitry 113. The pressure transducer 127 a comprises acommercially available silicone or other suitable plastic bridgepressure transducer that measures hydrostatic pressure to determinechanges in pressures as described below.

[0158] An elongate member 85 is affixed to an end of the capsule body81. Bipolar stimulation electrodes 86, 87 are located in a spaced apartrelationship, rearwardly on the elongate member 85. Conductors 95 extendthrough the flexible elongate member 85 connecting the electrodes 86, 87to the electronics 113. Opposing ends 92 a, 92 b of an inflatableballoon 92 are mounted forwardly of the electrodes 86, 87 on theflexible elongate tubular member 85 by a suitable adhesive (not shown).A balloon inflation/deflation lumen 94 is provided in the flexibleelongate member 85 and extends from the capsule body 81 to an inflationport 93 that opens into the interior of the balloon 92 as shown in FIG.22. The balloon inflation/deflation lumen 94 is coupled to the pressuretransducer 127 a so that compression pressures sensed by the balloon 92will be supplied to the pressure transducer 127 a as the pressure of thegas in the balloon 92 and the lumen 94 changes.

[0159] The capsule 80 includes a dissolvable encasing (not shown) of thesame type as the encasing 12 shown in FIG. 15. Similar to the encasingshown in FIG. 15, such an encasing would enclose the flexible elongatemember 85 including the inflatable balloon 92 and electrodes 86, 87 andwould dissolve, e.g. in the small intestine releasing the elongatemember 85 as illustrated in FIGS. 21 and 22.

[0160] A balloon inflator is provided within the capsule 80 comprising asmall canister 97 of compressed CO₂ or other suitable gas. The canister97 is coupled to the lumen 94 through a valve connection 98. Theoperation of the valve 98 is controlled by the electronics 113 through adriver 128 a, b, c, or d. When the flexible elongate member 85 isdeployed upon dissolving of the encasing, the electronics 113 cause thevalve 98 to open and inflate the balloon 92.

[0161] Alternatively, the balloon 92 can be pre-inflated with a gas orfluid before enclosure within the encasing. In this case, the inflationcanister 97 and valve 98 may be eliminated. The balloon 92 is formed ofa gas impermeable material so that it will remain inflated oversubstantial periods of time. The balloon may be formed, for example, ofpolyurethane, PET, nylon or polyethylene.

[0162] In a preferred operation and use, the capsules shown in thevarious embodiments in FIGS. 12 and 18-22, are used in conjunction withthe circuitry shown in FIG. 4 or FIG. 13 in small intestine electricalstimulation. A small intestine suited for treatment using the capsulemay be diseased and incapable of adequate contractile activity. Forexample the nerves of the small intestine may be compromised due togastric or diabetic neuropathy. Because of such a disorder, the patientmay have a motility disorder that would be advantageously treated usingsmall intestine electrical stimulation.

[0163] The stimulator capsule may also be used to measure otherelectrical characteristics such as EMG or impedance as described hereinwith respect to the electronic circuitry 113 show in FIG. 4. A patientwishing to treat a motility disorder ingests a capsule of the presentinvention near the beginning, midway, or following the ingestion offood. A capsule when ingested will travel through the esophagus into thestomach. Where a dissolvable encasing is utilized for encapsulating theelongate member and electrode(s), the encasing is readily dissolved bythe fluids within the stomach or duodenum, permitting the flexibleelongate member carrying the stimulation electrode to be deployed.

[0164] The capsule is preferably used with the tracking system describedherein where treatment is triggered by an external (telemetry) signalfrom the tracking device. A first capsule may be delivered and anelectrical parameter of the intestine may be mapped with respect to thelength of the intestine. A second capsule may be delivered and used toprovide electrical stimulation at an identified location along thelength of the tract. An external signal to the capsule signals when tobegin and end stimulation.

[0165] The electrical stimulation capsule may also be used independentof the tracking system. In a variation of the embodiment, the capsulecan be programmed to begin emitting electrical stimuli to one or morestimulation electrodes 16 a-c, and/or 17, within a predetermined timeafter ingestion, for example, within one to one and one-half hours afteringestion into the stomach, at which time it is most probable that thecapsule would have passed into the duodenum along with food materialpassing from the stomach. As an alternative, a single capsule maystimulate and measure the electrical parameters. The capsule may senseelectrical parameters and when a clinically undesirable electricalparameter is detected, the capsule may provide an appropriate electricalstimulation in response.

[0166] Such a system would have the advantage of not requiring externalgear such as the recorder and pods. Also, the capsule may be constructedto sense when it is in the duodenum, for example with a pH sensor or apressure sensor. Also, the electronics 113 can be triggered to commenceat the time the encasing is dissolved and the stimulation electrode isexposed to body fluids. Alternatively, electrical stimuli can betriggered by the electronics 113 to commence within a predetermined timeafter the encasing dissolves. In such case, the capsule is enclosed in agel material that dissolves after it leaves the stomach when it reachesthe small intestine. When triggered, electronic circuitry 113 initiateselectrical stimuli to the small intestine of the patient, at periodicintervals, such as, for example using one or more waveforms like thoseshown in FIGS. 17A and 17B.

[0167] Alternative electronic circuitry 313 illustrated in FIG. 23 maybe used with any of the stimulation capsules illustrated herein.According to an alternative embodiment, the electronic circuitry 313 isused in a simplified stimulation system. According to a preferredembodiment of the system, prior to each stimulation pulse or burst ofpulses the capsule receives basic instructions. The instructions may bea trigger signal to trigger a stimulation pulse or burst of pulses withpredetermined stimulation parameters, such as amplitude and pulse width,to be emitted by the capsule. The instructions may also includeinformation regarding the stimulation parameters for the pulses to beemitted. The instructions to trigger and/or specify a stimulation pulseor burst of pulses to be delivered to the intestinal wall aretelemetrically delivered to the electronic circuitry 313.

[0168] The electronic circuit 313 is simplified and includes amicroprocessor 312, ROM 315, RAM 316, a clock 311, a telemetry coil 335,a battery 314 a dc-dc converter for stimulation 330, a telemetrydetection circuit 317, and a pacing driver 318. The microprocessor 312is coupled to the ROM 315, which contains program instructions for themicroprocessor 312 and any other permanently stored information thatallows the microprocessor 312 to operate. ROM 315 may also containdefault and standard stimulation parameters. The microprocessor 312addresses memory in a location in the ROM 315 through address bus 315 aand the ROM 315 provides the stored program instructions to themicroprocessor 312 via data bus 315 b. The microprocessor is coupled tothe RAM 316 via an address bus 316 a for addressing a location in theRAM 316 and a bi-directional data bus 316 b for delivering informationto and from the RAM 316. The RAM 316 may be used by the microprocessor312 to store custom stimulation parameters sent via telemetry prior to aseries of stimulation pulses or bursts of pulses, or, just before eachstimulation pulse or burst of pulses. RAM 316 may also temporarily storean identification code to specify the already stored default, standardor custom stimulation parameters to be used for stimulating theintestinal wall.

[0169] The trigger signals for each stimulating pulse or burst of pulsesand the stimulation parameter instructions are supplied through thetelemetry coil 335 to the microprocessor 312 and are then deliveredthrough the pacing driver 318 in real time to the intestinal wall(through electrodes as described herein). Thus, the capsule itself doesnot direct the stimulation or the intestinal wall but receivesdirections from an external source and delivers stimulation accordinglyand in real time to the intestinal wall.

[0170] The embodiment of FIG. 23 could be further simplified byreplacing the microprocessor 312, ROM 315, RAM 316, and clock 311 withlogic gates or a state machine. In such variation, some or all of thestimulation parameters may be preset and stored in the hardware in thecapsule. For example, stimulation amplitudes could be stored as 5different states in a simple state machine. The telemetry instructionsignal could then consist of a simple pulse train that would representthe trigger signal as well as encode one of the five stimulationamplitudes while using an otherwise fixed stimulation pattern.

[0171] The electrical pulses provided by the electronics 113 through theelectrode pairs 16 a-c, 17 (as selected) (FIG. 15, 16); 56, 57 (FIG.18); 66, 67 (FIG. 19,20); 86, 87 (FIG. 21); and 116, 117 may be used tocreate peristaltic contractions in the wall to cause movement of foodmaterial along with the capsule in the intestine. In an alternativeembodiment where it is desired to retard motility in the smallintestine, inhibition of peristaltic contractions by electricalstimulation may be effected by delivering electrical pulses designed toinhibit or interfere with the inherent electrical potentials, resultingin failure of normal peristaltic contractile activity.

[0172] In certain situations with respect to motility disorders, it maybe desirable to supply synchronized stimulating pulses to the wall ofthe small intestine by the use of multiple pairs of stimulatingelectrodes such as, for example, a plurality of pairs similar toelectrodes 16 a-c carried on the flexible elongate tubular membersecured to the capsule as shown in FIG. 12 and synchronizing the pulsesin forward (aborad) or reverse (orad) directions in order to causeforward or reverse stimulation of the intestinal tract.

[0173] As the capsule passes along the intestinal tract, it continues tosupply successive stimuli through the intestine. The rapidity ofmovement of food material through the small intestine can be controlledby the stimulating parameters such as frequency or amplitude of thesignals utilized for supplying electrical stimuli or pulses to theintestinal tract. The capsule may provide certain stimulation patternsin the small intestine until it reaches the colon. (This may bedetermined by sensed electrical or other parameters, or by apredetermined time interval). At this time the electrical stimuli can beterminated or alternatively they can continue to be generated at thesame or different parameters as the capsule passes through the colonuntil it exits from the body through the rectum in a bowel movement.

[0174] Where it is necessary for the patient to ingest a capsule eachtime food is ingested by the patient, the patient can have additionalcapsules on hand and ingest a capsule with each meal.

[0175] The electrode configuration preferably comprises two separateelectrical elements forming electrically opposite bipolar electrodes.However, a monopolar or unipolar construction with a remote return isalso contemplated by the invention. Spacing of the bipolar electrodeelements from one another will preferably be about 5 mm. Electrodesformed on an elongate member will preferably be constructed from a metalwire or strip wound in a helical manner around the elongate tailportion. The electrode metal will preferably be corrosion resistant andbiocompatible such as Gold, Platinum, Titanium, etc. A helical windingpattern is preferred to provide an electrode that is more flexible thana solid cylinder, and thereby allow the elongate tail to be more easilywound or compressed for contairumnent in the dissolvable portion of thecapsule. An alternative construction is contemplated where the electrodeis embedded in an insulating polymer with an insulated lead extendingwithin or along the elongate member into the capsule body.

[0176] By varying the spacing between the stimulation electrodes or thesize of the electrodes, it is possible to change the current densitypassing through the wall of the intestine during stimulation. A devicemay be provided where electrodes may be selected to maximize theseparameters. For example a plurality of electrode pairs may be providedfrom which the optimal pair of electrodes may be selected. Alsoindividual electrodes may be configured to form a pair of bipolarelectrodes upon selection.

[0177] The electrical pulses or pulse train supplied to the stimulationelectrodes can be at suitable stimulation intervals as for example, inthe case of pacing type electrical stimulation, every few seconds up toten seconds in the small intestine or several hours in the colon.

[0178] In connection with the electrical stimulation functions describedherein, it is often desirable to measure the pressures which are createdby peristalsis of the intestinal contractions. Referring to FIGS. 21 and22, this can be readily measured by sensing the compressive forcesexerted on the balloon 92 with transducer 91. By sensing such pressuresand supplying the information by telemetry to the external recorder 105,it is possible to ascertain the efficacy of the stimulation beingapplied to the particular portion of the intestinal tract and ifnecessary to adjust the electrical stimulation parameters to create thedesired contractile forces being sensed by the balloon and the pressuretransducer. For example, if the sensed pressure indicates suboptimalcontractile response, the stimulation parameters may be adjusted, e.g.,telemetrically. If the existence of contractions is detected, thestimulation electrodes may be turned off. This may also serve toconserve battery power.

[0179] One method of use of a capsule of the present invention is insmall intestine electrical stimulation. Electronic circuitry is disposedwithin the capsule and creates electrical stimuli for causingperistaltic motion of the small intestine for causing pacing ofperistaltic motion in the small intestine. Other effects on theelectrical, chemical, and/or neural systems of the intestinal tract maybe achieved with electrical stimulation. One example includes anelectrical stimulus that is used to interfere with the naturalpacesetter potential and thus prevent organized intestinal tractcontractile activity from occurring.

[0180] Referring to FIGS. 24 and FIG. 11E, another embodiment of theinvention is illustrated. The capsule 190 comprises a capsule body 191containing components described above with various embodiments and withreference to FIG. 4. Electronics circuit 113, battery 114, RF coil 135and acoustic transducers 136 a-c are located in the housing 191. Theoptical detector 127 c comprises photo diode detectors 196, 197 and LEDlight source 199 (in this embodiment a white light source) located onthe housing 191 and coupled to the electronic circuit 113. The photodiode detectors may comprise an array of detectors of filters, eachsensing a particular wavelength or range of wavelengths of light. Sucharray is coupled to the processor 12 which selects the sensors orfilters that correspond to wavelength(s) to be detected, e.g., based ona selected diagnostic mode. The processor 122 may select a particularchemical, toxin tissue pathology, etc. for which to sense. This may bepreprogrammed into the processor or may be modified during the course oftreatment or diagnosis with the capsule system. This may also beactuated by an external controller or by a user/health care professional(e.g. who observing other sensed parameters) during the course ofdiagnosis and or treatment.

[0181] As described above, the electronics circuit 113 is configured toreceive sensed signal(s) indicative of optical parameter(s) such as onein which presence of blood is indicated. The sensed signal iscommunicated to the processor which communicates a signal representativeof the sensed information via the telemetry coil 135 to an externalcontroller/processor. The information may, for example, be in the formof a composite signal combining sensed light information of each of thesensors, or may be temporally spaced signals for each of the sensors.The LED light source 199 is controlled by the controller which directs abrief pulse of light into the intestinal tract or at the tissue of thewall of the intestinal tract. The photo diode dectors 196, 197 areselected to detect different wavelengths of light. The excitationcharacteristics of the object and/or the absorption of a particularwavelength (non-reflectance) of light to which a photo diode issensitive is determined when the photo diode senses or does not sense asufficient amount of light corresponding to a particular wavelength.Alternatively a plurality of LED emitters of predetermined wavelengths(e.g. with filters) may be used to illuminate the intestinal tract.Reflectance of the particular wavelength may be used or absorption ofthe wavelength may be used to determine presence or absence of variouscompounds or diseased tissues.

[0182]FIG. 11E illustrates one embodiment of an exemplary map of opticalwavelength sensing where reflectance of a wavelength correponding to thepresence of blood is shown. As illustrated the initial spike of thesensed wavelength occurs at position L1 indicating presence of blood. Asthe capsule moves distally from the source of the bleeding, as indicatedby the linear map, the presence of blood diminishes as the blood movesthrough the intestinal tract. FIG. 25 illustrates the absorbtivityspectra of hemoglobin. Thus according to one embodiment, sensors forsensing hemoglobin may sense a selected wavelength or wavelengths ofbetween about 540 to 620 nm.

[0183]FIG. 26 is a graph illustrating relative differences inabsorbtivity of oxygenated versus deoxygenated hemoglobin at differentwavelengths. Detecting deoxygenated hemoglobin may be used to identifydiseased tissue. For example, necrotic or ischemic tissue has absent ordiminishing blood flow. In one embodiment where necrotic or ischemictissue is present, this tissue may be sensed by determining a change inabsorption of light at a specific wavelength or wavelengths, e.g. about600 nm, as compared to the absorption of such wavelength or wavelengthsof light by healthy tissue. The change in absorption may illustratepresence of deoxygenated hemoglobin versus oxygenated hemoglobin and thepresence of an arterial blockage or other pathology where tissue may notbe receiving sufficient blood circulation.

[0184] The present invention provides an improved method and device fortracking an autonomous capsule as well as a method and device fortracking and diagnosing the gastrointestinal tract, preferably using atracking device. Various modifications and combinations are contemplatedby this invention and may be made without departing from the scope ofthe invention.

[0185] For example, in another embodiment of the tracking system, thedirection of the ultrasound signal used for locating the capsule isreversed. In this embodiment, the capsule receives the ultrasoundsignals generated by the pods and retransmits the signals on the RFcarrier back to the pods or external monitor. In this way, the capsuleposition may be located by measuring the time delay from transmission ofthe ultrasound signal(s) by the pod(s) to their reception by thecapsule. Rather than activating all pods simultaneously, each pod may besequentially activated to transmit ultrasound. Accordingly, the pod tocapsule path is identified by the time of transmission from a particularpod. When a single pod is activated in this way for transmission, allthe remaining pods may also be switched to receive the ultrasound signalfrom the transmitting pod. This allows the pod-to-pod delay times to bemeasured, so that the relative position of the pods can be determined onan ongoing basis.

[0186] If simultaneous transmission from all pods is desired, theultrasound signals from each pod may be separated by using a variety ofmethods. For example, each pod may generate a unique ultrasoundfrequency allowing the signals to be separated by filtering.

[0187] In one variation, for example, a continuous wave signal withamplitude modulation may be used rather than a narrower pulse. In suchvariation, time delays may be measured by measuring the phase of thereceived signals relative to the transmitted signal.

[0188] Alternative reference signals may be used to establish when theacoustic signal is transmitted. For example, an infra-red link or adistributed resistive link may be used. Infra-red links may beconstructed using light emitting diodes with an infra-red wavelengthchosen to minimized the effects of tissue/light attenuation. The lighttransmitters and sensors may be on the capsule and/or at the externallocation for one or two way signal transmission. The light may bemodulated with a high frequency carrier in a similar manner to an RFlink. The modulated light signal can then be detected after it haspassed through the tissue using a light sensor or sensors. A distributedresistive link may be used to directly couple an electrical carriersignal through the body to an external sensor or sensors, oralternatively or additionally from an external transmitter to electrodesensors coupled to the capsule. A small high frequency carrier,typically 100 kHz or above, is preferably chosen for the carrierfrequency to prevent any muscle stimulation by the carrier. The sensoron the capsule or at the external location would then detect the highfrequency carrier signal, which would be attenuated by the distributedresistive divider formed by the conductive body tissue. To transmit orreceive the signal to or from an external location, the external sourceor sensor would be coupled into the body via two skin electrodes, spacedat some distance apart. Electrodes on the capsule would be used toreceive (or transmit) such carrier signal. The high frequency carrierwould preferably be modulated in the same way as an RF link, usingamplitude, frequency or other modulation schemes as are well known inthe art. Preferably, the various signals e.g., going to or from thecapsule, would be placed on different carrier frequencies to allow foreasy separation via filtering, of the outgoing and incoming signals.

[0189] Further, as an alternative to using an externally detectablesignal such as an RF signal, as a reference signal to establish the timeat which the acoustic pulse is emitted, the ultrasound transmitters andreceivers may be configured to establish such transmission times andthus the location of the capsule. Based on the differential time betweentwo ultrasound receivers receiving an ultrasound pulse from a capsule,the possible location of the capsule may be defined by a paraboloidplane between the two receivers. Using more than two receivers,additional such paraboloid planes representing possible locations may bedetermined. The intersection of the planes provides information fromwhich the actual location of the capsule may be derived. By filteringout impossible locations (e.g., by knowing points that would lie outsidea patient's body, e.g., based on pod placement on a patient, or byadding additional pods for additional location information), the actuallocation of the capsule may be determined.

[0190] According to one variation, the differential distance isdetermined by multiplying the differential time between the reception ofthe ultrasound signal at one pod and the reception at the other podtimes the speed of sound in tissue. The possible location of the capsulebased on the derived differential distance is represented by aparaboloid plane between the two pods. When a third acoustic referencereceiver is added, the detected differential time between receiver oneand three and the differential time between receivers two and threeprovide additional paraboloid planes of possible capsule locations. Twoparaboloid planes intersect in a paraboloid or ellipsoid line;intersection with a third paraboloid plane defines one or more points ofpossible capsule locations. Strategic positioning of the acousticreference receivers, use of additional receivers and/or exclusion ofinvalid mathematical solutions (e.g. outside of the patient's body) mayenable a single solution to be obtained for capsule location.

[0191] The foregoing embodiments and variations of the invention areillustrative and not contemplated to be limiting, having been presentedby way of example. Numerous other variations and embodiments, as wouldbe apparent to one of ordinary skill in the art, are contemplated asfalling within the scope of the invention as defined by the claims andequivalents thereof.

What is claimed is:
 1. A system for diagnosing a gastrointestinalcondition comprising: an autonomous capsule sized to pass through theintestinal tract of a patient, the capsule comprising: a light sourceconfigured to emit light from the capsule; and a sensor configured tosense light at least one predetermined wavelength at a first locationwithin the intestinal tract and to output a signal representative oflight sensed by the sensor at the at least one predetermined wavelength;a processor coupled to the sensor to receive a signal representative oflight of the at least one predetermined wavelength sensed by the sensor,wherein the processor is configured to determine at least one conditionof: a presence of a substance, an absence of a substance, and acondition of tissue of the intestinal tract based at least in part onthe signal representative of light sensed by the sensor; and a capsuletracking system configured to track location of the capsule within anintestinal tract.
 2. The system for diagnosing the gastrointestinalcondition of claim 1 wherein the light source emits light at the leastone predetermined wavelength.
 3. The system for diagnosing thegastrointestinal condition of claim 1 wherein the capsule furthercomprises a filter coupled to the sensor, wherein the filter isconfigured to filter light into the sensor of the at least onepredetermined wavelength.
 4. The system of claim 1 wherein the capsuletracking system is configured to track location of the capsule within athree-dimensional coordinate system.
 5. The system of claim 4 whereinthe processor is coupled to the capsule tracking system to receiveinformation on the location of the capsule within the intestinal tract,and wherein the processor is arranged to identify the first location ofthe at least one condition within the portion of the intestinal tract.6. The system of claim 1 wherein the capsule tracking system isconfigured to track location of the capsule along a length of a portionof the intestinal tract.
 7. The system of claim 6 wherein the processoris coupled to the capsule tracking system to receive information on thelocation of the capsule within the intestinal tract, and wherein theprocessor is arranged to identify a location of a sensed condition alonga length of the portion of the intestinal tract.
 8. The system of claim6 further comprising a mapping element configured to map locations ofthe capsule along the length of the portion of the intestinal tract withrespect to conditions sensed by the sensor at corresponding locationsalong the length of the portion of the intestinal tract.
 9. The systemof claim 8 further comprising: a display coupled to the processor, thedisplay being configured to display a diagnostic map of sensed conditionof the intestinal tract along the length of the portion of theintestinal tract.
 10. The system of claim 6 wherein the capsule trackingsystem is arranged to determine capsule location along the length theportion of the intestinal tract, from a determination of a plurality oflocations of the capsule as the capsule passes through the portion ofthe intestinal tract.
 11. The system of claim 1 wherein the capsuletracking system comprises: an acoustic transducer transmitter and anacoustic transducer receiver, wherein the acoustic transmitter isarranged to transmit a tracking signal from the acoustic transmitter tothe acoustic receiver, between the autonomous capsule and a locationexternal to a patient's body, and wherein in use, the acoustictransmitter is located at one of the autonomous capsule and the locationexternal the patient's body and the acoustic receiver is located at theother of the autonomous capsule and the location external the patient'sbody.
 12. The system of claim 1 wherein: the capsule tracking systemcomprises: a plurality of acoustic transducers at the capsule, each ofthe plurality of acoustic transducers being arranged to emit an acousticsignal detectable externally of a patient's body as the capsule passesthrough at least a portion of the intestinal tract; and at least oneexternal acoustic receiver configured to sense the acoustic signaltransmitted by the capsule, wherein the acoustic signal of each of theplurality of acoustic transducers provides information from which thelocation of the capsule may be derived.
 13. The system of claim 1wherein the capsule further comprises: a telemetry device arranged totransmit a telemetry signal corresponding to the light sensed by thesensor, and a telemetry receiver for receiving the telemetry signal. 14.The system of claim 13 wherein the processor is located in an externaldevice coupled to the telemetry receiver.
 15. The system of claim 1wherein the capsule further comprises a marking mechanism configured tomark an identified location of a sensed condition within the intestinaltract.
 16. The system of claim 15 wherein the marking mechanismcomprises a substance release mechanism.
 17. The system of claim 16wherein the substance release mechanism comprises a dye releasemechanism.
 18. The system of claim 15 wherein the marking mechanismcomprises a position anchoring mechanism.
 19. The system of claim 1wherein the at least one condition comprises: presence of blood.
 20. Thesystem of claim 1 wherein the at least one condition comprises: absenceof blood in tissue
 21. The system of claim 1 wherein the at least onecondition comprises: presence of ischemic tissue.
 22. The system ofclaim 1 wherein the at least one condition comprises: presence ofnecrotic tissue.
 23. The system of claim 1 wherein the condition is thepresence or absence of hemoglobin.
 24. The system of claim 1 wherein theat least one predetermined wavelength is within a range of wavelengthsof between about 540 nanometers and about 620 nanometers.
 25. The systemof claim 1 further comprising a treatment capsule configured to treatthe condition determined by the capsule.
 26. The system of claim 25wherein the treatment capsule comprises a treatment capsule trackingsystem configured to track the location of the capsule and identify thelocation of the condition determined by the capsule.
 27. The system ofclaim 26 wherein the treatment capsule tracking system is configured totrack the location of the treatment along the length of at least aportion of the intestinal tract.
 28. A system for treating or diagnosingthe intestinal tract of a patient comprising: capsule means for movingthrough a portion of an intestinal tract; means for determining locationof the capsule means within a portion of the intestinal tract; lightemitting means for emitting a light at least one wavelength opticalsensing means for sensing an optical characteristic of the intestinaltract; tracking means for tracking the capsule means at a plurality oflocations and for tracking a sensed optical characteristic at theplurality of locations; and a processing means for determining acondition within the portion of the intestinal tract based at least inpart on the optical characteristic sensed at the plurality of locations29. The system of claim 28 wherein the means for determining location ofthe capsule means comprises an acoustic means for determining location.30. The system of claim 28 wherein the means for determining location ofthe capsule means comprises means for determining location of thecapsule means along a length of the portion of the intestinal tract. 31.The system of claim 28 further comprising a mapping means for mappinglocations of the capsule along the length of the portion of theintestinal tract with respect to conditions determined by the processormeans corresponding to at corresponding locations of the conditionsalong the length of the portion of the intestinal tract.
 32. The systemof claim 28 wherein the condition is selected from a group comprising: apresence of a substance, an absence of a substance, and a tissuecondition.
 33. The system of claim 28 wherein the condition is presenceof blood.
 34. The system of claim 28 wherein the condition is absence ofblood in tissue.
 35. The system of claim 28 wherein the condition is thepresence of ischemic tissue.
 36. The system of claim 28 wherein thecondition is the presence of necrotic tissue.
 37. The system of claim 28wherein the at least one predetermined wavelength is within a range ofwavelengths of between about 540 nanometers and about 620 nanometers 38.A method for diagnosing a condition of a gastrointestinal tractcomprising the steps of: providing an autonomous capsule comprising alight source and an optical sensor configured to sense light of at leastone predetermined wavelength; emitting light from the capsule in anintestinal tract; sensing light of the at least one predeterminedwavelength with the optical sensor at a location within a portion of agastrointestinal tract; and determining whether determine at least onecondition exists at the location, the condition being selected from: apresence of a substance, an absence of a substance, and a condition oftissue of the intestinal tract, and the condition determined at least inpart from the signal representative of light sensed by the sensor. 39.The method of claim 38 further comprising the steps of: sensing light ata plurality of locations along a length of a portion of agastrointestinal tract; and mapping sensed condition with respect toeach of the plurality of locations along the length of thegastrointestinal tract.